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Transcript
KUOPION YLIOPISTON JULKAISUJA D. LÄÄKETIEDE 439
KUOPIO UNIVERSITY PUBLICATIONS D. MEDICAL SCIENCES 439
PÄIVI MAARANEN
Dissociation in the
Finnish General Population
Doctoral dissertation
To be presented by permission of the Faculty of Medicine of the University of Kuopio
for public examination in Auditorium L21, Snellmania building, University of Kuopio,
on Friday 26 th September 2008, at 12 noon
Department of Psychiatry
University of Kuopio and
Kuopio University Hospital
JOKA
KUOPIO 2008
Distributor : Kuopio University Library
P.O. Box 1627
FI-70211 KUOPIO
FINLAND
Tel. +358 40 355 3430
Fax +358 17 163 410
www.uku.fi/kirjasto/julkaisutoiminta/julkmyyn.html
Series Editors: Professor Esko Alhava, M.D., Ph.D.
Institute of Clinical Medicine, Department of Surgery
Author´s address: Department of Psychiatry
Kuopio University Hospital
P.O.Box 1777
FI-70211 KUOPIO
Tel. +358 17 175 226
Fax +358 17 175 391
Supervisors: Professor Heimo Viinamäki, M.D., Ph.D.
Department of Psychiatry
University of Kuopio and Kuopio University Hospital
Reviewers: Docent Hannu Lauerma, M.D., Ph.D.
Department of Psychiatry
University of Turku
Docent Juha Veijola, M.D., Ph.D.
Department of Psychiatry
University of Oulu
Opponent: Professor Simo Saarijärvi, M.D., Ph.D.
Department of Psychiatry
University of Turku
Professor Raimo Sulkava, M.D., Ph.D.
School of Public Health and Clinical Nutrition
Professor Markku Tammi, M.D., Ph.D.
Institute of Biomedicine, Department of Anatomy
Docent Antti Tanskanen, M.D., Ph.D.
Department of Psychiatry
University of Kuopio
ISBN 978-951-27-0959-5
ISBN 978-951-27-1056-0 (PDF)
ISSN 1235-0303
Kopijyvä
Kuopio 2008
Finland
Maaranen, Päivi. Dissociation in the Finnish general population. Kuopio University Publications D. Medical
Sciences 439. 2008. 97 p.
ISBN 978-951-27-0959-5
ISBN 978-951-27-1056-0 (PDF)
ISSN 1235-0303
Abstract
The aim of this epidemiological study was to investigate the prevalence of psychological and somatoform
dissociation and associated factors in the general population. The course of psychological dissociation was examined in
a three-year follow-up study. Dissociation was measured with the Dissociative Experiences Scale (DES) and its
subscale for pathological dissociation, the Dissociative Experiences Scale Taxon (DES-T), and with the Somatoform
Dissociation Questionnaire (SDQ-20).
Participants in the study (n = 3004) were derived from a random sample of general population adults (25-64 years
old) in eastern Finland. The data were gathered by postal questionnaires in 1998, 1999 and 2001. The response rate was
68% at baseline, and 75% of the baseline respondents returned the questionnaire on three-year follow-up in 2001.
The prevalence of pathological dissociation (DES-T •20) was 3.4% in the general population, and there was no
association between pathological dissociation, gender or age. Single, divorced or widowed subjects were more often
high dissociators. Frequent alcohol consumption, a poor financial situation and a reduced working ability were
associated with pathological dissociation. The cross-sectional association between pathological dissociation, depression,
alexithymia and suicidal ideation was estimated as strong.
The prevalence of somatoform dissociation (SDQ-20 •30) was 9.4% in the general population. Unemployment, a
reduced working ability and a poor financial situation were associated with high somatoform dissociation. There was a
graded relationship between high somatoform dissociation and an increasing number of adverse childhood experiences
(ACEs). Of the individual ACEs, childhood physical punishment was associated with high somatoform dissociation.
A decile of the sample was investigated to assess the relationship between psychological and somatoform
dissociation. Those with both high psychological and high somatoform dissociation clearly differed from the other
groups: they had more depressive symptoms and more frequently reported suicidal ideation, a reduced working ability,
a poor financial situation, poor general health and inadequate social support than subjects in the other groups. The
correlation between the DES and SDQ-20 scores was 0.60, indicating common background factors for the two domains
of dissociative experiences.
In the follow-up study, of the 98 high dissociators at baseline, 28 subjects (29%) were stable high dissociators (DES
•20), while among 70 subjects (71%) the DES score declined below the cut-off score. Of the healthy participants at
baseline, 28 (2%) became new high dissociators, while 1371 (92%) out of the total cohort of 1497 participants were
constantly low dissociators. Dissociative taxon membership was detected in 39 subjects either at baseline or on followup, but only four of them met the criteria in both assessments. Stable high dissociation was associated with an increase
in the BDI score on follow-up, baseline suicidal ideation, a younger age, a reduced working ability and smoking. Risk
factors for becoming a new high dissociator were an increase in the BDI score, a younger age at baseline and a reduced
working ability. Among the baseline high dissociators, recovery from high dissociation was associated with a decline in
the BDI score on follow-up, and with no suicidal thoughts, older age and a good working ability at baseline.
This study provided new information on the prevalence and stability of dissociation and associated factors in the
general population. The comorbity of dissociative symptoms should be noted among depressive and suidical patients in
clinical practice.
National Library of Medicine Classification: QZ 53, WA 900, WA 950, WM 141, WM 170, WM 171, WM 173.6,
WM 270
Medical subjects headings: Age Factors; Comorbidity; Cross-Sectional Studies; Demography;
Depression/epidemiology; Depressive Disorder/epidemiology; Dissociative Disorders/epidemiology; Domestic
Violence; Employment; Family Health; Finland/epidemiology; Follow-Up Studies; Health Status; Health Surveys; Life
Change Events; Population Surveillance/methods; Prevalence; Prospective Studies; Psychiatric Status Rating Scales;
Questionnaires; Risk Factors; Sex Factors; Social Support; Somatoform Disorders/epidemiology; Substance-Related
Disorders/epidemiology; Suicide, Attempted/statistics & numerical data; Suicide/psychology; Work Capacity
Evaluation
Maaranen, Päivi. Dissosiaatio suomalaisessa yleisväestössä. Kuopion yliopiston julkaisuja D. Lääketiede
439. 2008. 97 s.
ISBN 978-951-27-0959-5
ISBN 978-951-27-1056-0 (PDF)
ISSN 1235-0303
Tiivistelmä
Tämä neljästä eri osajulkaisusta koostuva väitöskirjatyö pohjautuu Kuopion yliopistollisen sairaalan psykiatrian
klinikassa toteutettuun yleisväestön mielenterveyttä kartoittavaan alueelliseen yleisväestöotokseen. Väestöotokseen
valittiin satunnaisesti 25-64-vuotiaita aikuisia (n = 3004). Itse täytettävien tutkimuslomakkeiden avulla saatu tieto
kerättiin postikyselynä vuosina 1998, 1999 ja 2001. Epidemiologisen tutkimuksen tavoitteena oli tutkia psykologisen ja
somatoformisen dissosiaation vallitsevuutta ja niihin yhteydessä olevia tekijöitä. Psykologisen dissosiaation kulkua
mitattiin lisäksi kolmen vuoden seurantatutkimuksella. Dissosiaation mittamiseen käytettiin itsetäytettäviä mittareita:
Dissociative Experiences Scale (DES) - asteikkoa, siitä johdettua patologista dissosiaatiota mittaava Dissociative
Experiences Scale Taxon (DES-T) - asteikkoa ja Somatoform Dissociation Questionnaire (SDQ-20) - mittaria.
DES-T-mittarilla mitattuna patologisen dissosiaation prevalenssi yleisväestössä oli 3.4%, johon iällä tai
sukupuolella ei ollut merkittävää vaikutusta. Patologiseen dissosiaatioon yhteydessä olevina taustatekijöinä nousi esille
alkoholinkäyttö, huono taloudellinen tilanne ja alentunut työkyky. Yksin asuvilla, eronneilla tai leskillä patologinen
dissosiaatio oli yleisempää kuin parisuhteessa elävillä. Psykiatriset muuttujat, aleksitymia, depressio ja itsetuhoisuus,
olivat voimakkaasti yhteydessä patologiseen dissosiaatioon poikkileikkaustutkimuksessa (osajulkaisu I).
Somatoformista dissosiaatiota mitattiin SDQ-20-mittarilla, ja sen prevalenssi yleisväestössä oli 9.4%.
Somatoforminen dissosiaatio lisääntyi iän myötä ja se oli yleisempää miehillä. Siihen yhteydessä olevia tekijöitä olivat
työttömyys, alentunut työkyky ja huono taloudellinen tilanne. Lapsuuden ajan haitallisilla kokemuksilla oli yhteys
somatoformiseen dissosiaatioon: useamman lapsuudenaikaisen haitallisen kokemuksen yhtäaikainen esiintyminen oli
yhteydessä kohonneeseen somatoformiseen dissosiaatioon ja yksittäisistä muuttujista lapsen fyysinen rankaiseminen
ennusti aikuisiän kohonnutta riskiä somatoformiseen dissosiaatioon. (osajulkaisu II).
Psykologisen ja somatoformisen dissosiaation välisen suhteen tarkemmaksi tutkimiseksi väestöotoksesta poimittiin
yhtä suuret ryhmät korkeimpia pisteitä saaneista henkilöistä kahdella dissosiaatiota mittaavalla asteikolla (DES ja SDQ20). Tämä kahden dissosiaation komorbidi ryhmä havaittiin muista selvästi poikkeavaksi: heillä esiintyi merkittävästi
enemmän depressio-oireita ja itsetuhoajatuksia. Lisäksi heillä oli alentunut työkyky, huono taloudellinen tilanne,
huonoksi koettu terveydentila ja riittämättömästi sosiaalista tukea verrattuna muihin ryhmiin. Psykologisen ja
somatoformisen dissosiaation välinen korrelaatio havaittiin sinällään merkittäväksi (osajulkaisu III).
Kolmen vuoden seurantatutkimuksessa lähtötilanteen 98:sta korkeasti dissosioivasta henkilöstä DES-mittarilla
mitattu psykologinen dissosiaatio oli pysyvää vain 28 henkilöllä (29%), 70 henkilöllä (71%) DES-pisteet laskivat
katkaisurajana käytetyn 20 pisteen alle. Alkuvaiheen terveistä henkilöistä (n = 1399) 28:lla henkilöllä (2%) pisteet
vastaavasti nousivat katkaisurajan yli, ja pysyvästi matalat DES-pisteet oli koko seurannan ajan 1371 henkilöllä (92%).
Pysyvä korkea dissosiaatio oli yhteydessä BDI-pisteiden lisääntymiseen seuranta-aikana, itsetuhoisuuteen, nuoreen
ikään, alentuneeseen työkykyyn ja tupakointiin. DES-Taxon-mittarin avulla laskettuun patologisesti dissosioivien
luokkaan kuului koko tutkimuksessa 39 henkilöä, mutta vain neljällä henkilöllä tämä ominaisuus oli pysyvä. Tämän
tutkimuksen perusteella DES-Taxon luokkaan kuuluminen eri mittausajankohdissa ei kuvannut pysyvää ilmiötä.
Tässä tutkimuksessa saatiin uutta tietoa dissosiaation vallitsevuudesta ja pysyvyydestä sekä niihin liittyvistä
tekijöistä suomalaisessa yleisväestössä. Dissosiaatio-oireiden tunnistaminen komorbidien depressio-oireiden ja
itsemurha-ajatusten yhteydessä tulisi ottaa huomioon myös kliinisessä työssä.
Yleinen suomalainen asiasanasto: dissosiaatiohäiriö;
mielenterveyshäiriöt; suomalaiset; tunne-elämän häiriöt
epidemiologia;
kyselytutkimus;
mielenterveys;
To my family
Acknowledgements
This thesis is based on a longitudinal project, the Kuopio Depression (KUDEP) study, carried
out at the Department of Psychiatry, Kuopio University Hospital between 1998 and 2001. I want to
express my gratitude to all the participants in the general population survey. Without their
collaboration, this study would not have been possible or successfully accomplished.
I wish to express my sincere gratitude to my principal supervisor, Professor Heimo Viinamäki,
who has provided the facilities to perform this study. His tireless optimism, enthusiastic guidance
and practical knowledge of writing scientific articles have provided support in carrying out all
phases of my thesis.
I owe my deepest gratitude to my supervisor, Docent Antti Tanskanen, who proposed the topic
of this thesis to me and introduced me to the world of scientific research. His pioneering work on
dissociation and psychic traumatization made it possible to perform this thesis as part of the
KUDEP project. It has been a privilige to work under his expert, intelligent and encouraging
guidance. He has always been able to arrange time for appointments and discussions, even during
the last few years after he moved to Helsinki.
I am grateful to the official reviewers of the thesis, Docent Hannu Lauerma and Docent Juha
Veijola, for their valuable suggestions and advice for the improvement of this thesis.
I am very grateful to my co-authors, head nurse Kaisa Haatainen, Professor Jukka Hintikka,
Docent Kirsi Honkalampi, and Professor Heli-Koivumaa-Honkanen. They each have helped me
during this study: in scientific writing, statistical issues and giving valuable opinions from other
aspects of this project.
For statistical advice I am thankful to Vesa Kiviniemi and Marja-Leena Hannila from the Center
of Statistical and Mathematical Services at the University of Kuopio. I wish to thank Roy Siddall
for his excellent work in revising the English manuscripts. I thank secretary Eeva-Maija Oittinen for
her friendly advice and practical help with the preparation of this thesis.
I wish to thank all my friends and colleagues in the Department of Psychiatry, Kuopio University
Hospital, for collaboration and support during the process of completing this thesis. I warmly thank
my secretary Sari Alismaa for being next door to my office and providing endless good humor and
secreterial advice during the last phases of my work. I am especially grateful to retired head
physician Juha Jääskeläinen for his encouragement to begin my scientific work, and Docent Pirjo
Saarinen for her support as the head physician during the process of preparing this thesis. I am
grateful to Professor Johannes Lehtonen for the facilities to carry out the work in this thesis and for
his interest in my scientific work on dissociation.
It has been a great opportunity for me to be part of a two-year education program by
Traumaterapiakeskus in Helsinki in 2006-2008. This education program introduced the participants
to the Theory of Structural Dissociation and phase-oriented treatment of complex trauma-related
disorders. This education has been invaluable to me in understanding trauma and dissociation, and
learning diagnostic tools as well as psychotherapeutic treatment methods for dissociative disorders.
I wish to express my sincere gratitude to Anne Suokas-Cunliffe for organizing this education
project and to all my teachers: Suzette Boon, Ellert Nijenhuis, Kathy Steele, and Onno van der Hart.
I am very grateful to my dear friends Hannele and Maarit for being there for me. We have been
friends since the beginning of our medical studies, and shared countless things in our personal and
professional life during the university years and after that together.
I warmly thank my parents, Mirja and Aimo Hujanen, for their love and support. They have
always encouraged me to learn and study. Their help in countless practical things has been
invaluable to me during this process. To my brother Pasi and his wife Minna and their children
Roosa and Roope, many thanks for sharing many happy moments together. Finally, I wish to
express my deepest gratitude to my husband Aki and to my children Iida and Akseli for all that love
and happiness you have brought me. Special thanks to Iida for discussions about writing and also
for helping me arrange the references.
Kuopio, August 2008
Päivi Maaranen
Abbreviations
ACE
Adverse Childhood Experience
A-DES
The Adolescent Dissociative Experiences Scale
ANP
Apparently Normal part of the Personality
APA
American Psychiatric Association
BDI
Beck Depression Inventory
CI
Confidence interval
DD
Dissociative Disorder
DES
Dissociative Experiences Scale
DES-ABS
Absorption and imaginative involvement factor of the Dissociative
Experiences Scale
DES-AMN
Amnestic factor of the Dissociative Experiences Scale
DES-DD
Depersonalization-derealization factor of the Dissociative Experiences
Scale
DES-NP
Non-pathological dissociation
DES-T
Subscale of the Dissociative Experiences Scale measuring pathological
dissociation (DES-Taxon)
DID
Dissociative Identity Disorder
DIS-Q
Dissociation Questionnaire
DSM
Diagnostic and Statistical Manual of Mental disorders
EP
Emotional part of the Personality
ICD
International Classification of Diseases and Related Health Problems
OR
Odds Ratio
PTSD
Post-traumatic Stress Disorder
SCID-D
Structured Clinical Interview for Dissociative Disorders
SD
Standard Deviation
SDQ-20
Somatoform Dissociation Questionnaire
SDQ-5
Screening version of the Somatoform Dissociation Questionnaire
SPSS
Statistical Package for the Social Sciences
TAS-20
The Toronto Alexithymia Scale
List of original publications
Original publications are referred to in the text by the Roman numerals I-IV.
I
Maaranen P., Tanskanen A., Honkalampi K., Haatainen K., Hintikka J., Viinamäki H.
Factors associated with pathological dissociation in the general population. Australian
and New Zealand Journal of Psychiatry 2005; 39:387-394.
II
Maaranen P., Tanskanen A., Haatainen K., Koivumaa-Honkanen H., Hintikka J.,
Viinamäki H. Somatoform dissociation and adverse childhood experiences in the
general population. Journal of Nervous and Mental Disease 2004; 192:337-342.
III
Maaranen P., Tanskanen A., Haatainen K., Honkalampi K., Koivumaa-Honkanen H.,
Hintikka J., Viinamäki H. The relationship between psychological and somatoform
dissociation in the general population. Journal of Nervous and Mental Disease 2005;
193:690-692.
IV
Maaranen P., Tanskanen A., Hintikka J., Haatainen K., Honkalampi K., KoivumaaHonkanen H., Viinamäki H. The course of dissociation: a 3-year follow-up study.
Comprehensive Psychiatry 2008; 49:269-274.
The original papers have been reproduced with the permission of the publishes.
CONTENTS
1. INTRODUCTION ...................................................................................................................................................... 19
2. REVIEW OF THE LITERATURE .......................................................................................................................... 20
2.1. HISTORY ............................................................................................................................................................... 20
2.1.1. Hypnosis ....................................................................................................................................................... 22
2.1.2. Towards the 21st century .............................................................................................................................. 23
2.2. DEFINITIONS OF DISSOCIATION ........................................................................................................................... 24
2.2.1. Dissociation as a defence mechanism ......................................................................................................... 25
2.2.2. Cognitive theory............................................................................................................................................ 26
2.2.3. Dissociation as a symptom ........................................................................................................................... 27
2.2.3.1. Psychological dissociative symptoms.....................................................................................................................27
2.2.3.2. Somatoform dissociative symptoms.......................................................................................................................28
2.2.3.3. Dissociative symptoms according to the Structural Dissociation Theory...........................................................29
2.2.4. Dimensional or categorical construct?........................................................................................................ 31
2.2.5. Dissociation as a disorder and the classification of dissociative disorders................................................. 33
2.3. BIOLOGICAL FACTORS IN DISSOCIATIVE PATHOLOGY........................................................................................ 36
2.4. ASSESSMENT OF DISSOCIATIVE SYMPTOMS WITH QUESTIONNAIRES ................................................................. 37
2.4.1. The Dissociative Experiences Scale (DES) ................................................................................................. 37
2.4.2. The Somatoform Dissociation Questionnaire (SDQ-20) ............................................................................ 38
2.4.3. Other measures............................................................................................................................................. 39
2.4.3.1. The Dissociation Questionnaire (DIS-Q)...............................................................................................................39
2.4.3.2. The Adolescent Dissociative Experiences Scale (A-DES) ....................................................................................40
2.4.3.3. The Multidimensional Inventory of dissociation (MID) ......................................................................................40
2.5. DISSOCIATION IN THE GENERAL AND NON-CLINICAL POPULATION ................................................................... 40
2.5.1. Prevalence of dissociative symptoms in general and non-clinical populations.......................................... 40
2.5.1.1. Prevalence of psychological dissociation ...............................................................................................................40
2.5.1.2 Prevalence of somatoform dissociation ..................................................................................................................41
2.5.2. Factors associated with dissociation............................................................................................................ 43
2.5.2.1. Sociodemographic factors ......................................................................................................................................43
2.5.2.1.1. Age ...................................................................................................................................................................43
2.5.2.1.2. Sex....................................................................................................................................................................43
2.5.2.1.3. Sosioeconomic and marital status.....................................................................................................................43
2.5.2.2. Adverse Childhood Experiences ............................................................................................................................44
2.5.2.3. Other psychiatric conditions ..................................................................................................................................45
2.5.2.3.1. Depression and suicidality ................................................................................................................................45
2.5.2.3.2. Other psychiatric disorders ...............................................................................................................................46
2.5.2.4. Alexithymia .............................................................................................................................................................47
2.5.2.5. Substance use (alcohol and tobacco)......................................................................................................................49
2.5.2.6. Familiality................................................................................................................................................................49
2.5.3. The relationship between psychological and somatoform dissociation...................................................... 50
2.5.4. Stability of dissociative symptoms ................................................................................................................ 50
3. AIMS OF THE STUDY ............................................................................................................................................. 52
4. PARTICIPANTS AND METHODS ......................................................................................................................... 53
4.1. STUDY DESIGN ...................................................................................................................................................... 53
4.2. STUDY POPULATION ............................................................................................................................................. 54
4.2.1. Study I........................................................................................................................................................... 54
4.2.2. Study II ......................................................................................................................................................... 55
4.2.3. Study III........................................................................................................................................................ 55
4.2.4. Study IV ........................................................................................................................................................ 55
4.3. METHODS.............................................................................................................................................................. 56
4.3.1. The assessment of dissociation .................................................................................................................... 56
4.3.1.1. The Dissociative Experiences Scale (DES) ............................................................................................................57
4.3.1.2. The Somatoform Dissociation Questionnaire (SDQ-20) ......................................................................................57
4.3.2. Depression .................................................................................................................................................... 58
4.3.3. Suicidal ideation........................................................................................................................................... 58
4.3.4. Alexithymia................................................................................................................................................... 59
4.3.5. Adverse childhood experiences (ACEs) ....................................................................................................... 59
4.3.6. Statistical analysis ........................................................................................................................................ 60
5. RESULTS .................................................................................................................................................................... 62
5.1. PATHOLOGICAL DISSOCIATION (STUDY I)........................................................................................................... 62
5.1.1. The prevalence of pathological dissociation and mean scores of the DES in the general population...... 62
5.1.2. Factors associated with pathological dissociation....................................................................................... 62
5.2. SOMATOFORM DISSOCIATION (STUDY II) ........................................................................................................... 63
5.2.1. The prevalence of somatoform dissociation and the mean scores of the SDQ-20 in the general population
................................................................................................................................................................................ 63
5.2.2. Sociodemographic variables ........................................................................................................................ 63
5.2.3. Adverse childhood experiences (ACEs) ....................................................................................................... 63
5.3. THE RELATIONSHIP BETWEEN PSYCHOLOGICAL AND SOMATOFORM DISSOCIATION (STUDY III).................... 64
5.4. COURSE OF DISSOCIATION IN THE GENERAL POPULATION (STUDY IV) ............................................................. 65
5.4.1. Stability of psychological dissociative symptoms......................................................................................... 65
5.4.2. Associations between dissociation, depressive symptoms and suicidal ideation ........................................ 65
6. DISCUSSION.............................................................................................................................................................. 67
6.1. PREVALENCE OF DISSOCIATION IN THE GENERAL POPULATION ........................................................................ 67
6.2. FACTORS ASSOCIATED WITH DISSOCIATION ....................................................................................................... 68
6.2.1. Age ................................................................................................................................................................ 68
6.2.2. Sex................................................................................................................................................................. 69
6.2.3. Socioeconomic and marital status ............................................................................................................... 69
6.2.4. Substance use (alcohol and tobacco)........................................................................................................... 70
6.3. COMORBIDITY BETWEEN DISSOCIATION, DEPRESSIVE SYMPTOMS AND SUICIDAL IDEATION ........................... 70
6.3.1. Comorbidity between dissociative experiences and depressive symptoms .................................................. 71
6.3.2 The relationship between psychological and somatoform dissociation....................................................... 73
6.3.3. The relationship between dissociation and suicidal ideation...................................................................... 73
6.4. THE RELATIONSHIP BETWEEN DISSOCIATION AND ALEXITHYMIA ..................................................................... 74
6.5. THE IMPACT OF ADVERSE CHILDHOOD EXPERIENCES (ACES) ON SOMATOFORM DISSOCIATION .................... 76
6.6. THE STABILITY OF DISSOCIATIVE SYMPTOMS ..................................................................................................... 77
6.7. A CATEGORICAL OR DIMENSIONAL CONSTRUCT?............................................................................................... 78
6.8. METHODOLOGICAL CONSIDERATIONS ................................................................................................................ 79
6.8.1. Study population and design........................................................................................................................ 79
6.8.2. The Dissociative Experiences Scale and Somatoform Dissociation Questionnaire................................... 80
6.8.3. Other measures............................................................................................................................................. 81
7. CONCLUSIONS......................................................................................................................................................... 82
7.1. CONCLUSIONS FROM THE RESULTS ..................................................................................................................... 82
7.2. SUGGESTIONS FOR FUTURE RESEARCH................................................................................................................ 82
7.3. CLINICAL IMPLICATIONS ..................................................................................................................................... 83
REFERENCES ............................................................................................................................................................... 84
Tables
Table 1.
The phenomenological categorization of dissociative symptoms (Van der Hart et al.,
2006).
Table 2.
A synopsis of the classification of dissociative disorders with comparisons between
the ICD-10 and DSM-IV-TR.
Table 3.
Prevalence of high dissociation and mean scores from questionnaires on dissociation
in non-clinical population samples.
Table 4.
The relationship between dissociation and alexithymia in clinical and non-clinical
samples.
Table 5.
Sociodemographic characteristics of the subjects in studies I-IV.
Figure
Figure 1.
Formation of the study population.
Appendices
Appendix I Dissociative Experiences Scale
Appendix II Somatoform Dissociation Questionnaire
19
1. Introduction
In the past two decades, the debate over dissociation and dissociative disorders has been
accompanied by an increase in the number of studies and articles on dissociation. This surge
follows a long history of clinicians and researchers simply seeking to evidence the existence of
dissociative phenomena. Early endeavours to document dissociative phenomena were often based
on case study descriptions and philosophical musings (Rieber, 2002). Many of the ideas of the early
theorists who grappled with dissociative phenomena are quite relevant today.
As the concept of dissociation has gained traction in mainstream psychology and psychiatry in
recent years, empirical investigation has enhanced our understanding of the complexity of
dissociative phenomena. Definitional issues are of central importance to both theory building and
empirical investigation. As the field grows, delineating and clarifying definitional issues, such as
whether dissociation is premised to be a state or trait, a continuum or a taxon, or some combination,
is of critical importance. Theory building, assessments and data interpretation all inherently depend
on answers to these questions (DePrince and Cromer, 2006). Our studies on dissociation in the
general population provide some answers to these issues.
Somatoform dissociation has gained significance in research on dissociation through the work of
Ellert Nijenhuis and his Dutch colleagues. They have described the phenomenology of somatoform
dissociation and its relationship with various traumatic experiences. They have constructed
psychometrically sound instruments for measurement and have developed an important theoretical
perspective (Nijenhuis, 2000; Nijenhuis et al., 1996, 1998a, 1999). The categorization of conversion
and dissociative disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV),
and whether they should be placed in the same category of dissociative disorders, is being evaluated
in the development of DSM-V. However, epidemiological studies in the general population on
somatoform dissociation or on the relationship between psychological and somatoform dissociation
have been lacking.
20
2. Review of the literature
2.1. History
Known from Pharaonic Egypt and Greece, hysteria had been considered a disease of somatic
nature and origin. ‘Hysteria’ is derived from the Greek word ‘hystera’, which means ‘uterus’, and
hysteria has traditionally been identified as a disease of women. The Greek theories about hysteria
were influenced by the Egyptian wandering womb hypothesis. Hippocrates (460-370 B.C.) located
mental disorders in the brain, but he thought that hysteria was a disorder of uterine origin. The
Greeks blamed celibacy for causing the womb to become lighter so that it would ascend into the
abdomen. Various suggestions for treatment included bandaging below the hypocondrium to
prevent further upward wandering, and marrying in order to become pregnant (Fink, 1996).
In the Medieval era, many illnesses and cures were attributed to sorcery, witchcraft and saints,
and little distinction was made between medical, neurological and psychological disorders. Social
attitudes toward hysteria changed; the preoccupation with demonology and witchcraft altered
societal perceptions of a hysteric from that of a sick human being to that of someone who was
deliberately possessed by the devil (Fink, 1996). With the rise of Christianity, organic theories of
hysteria were replaced by supernatural explanations and unusual female complaints were seen to be
the work of the devil (Acocella, 1999). Such beliefs led to the infamous Witch Trials, and the fate
of hysterics was similar to that of the organically ill.
Neuroanatomist Thomas Willis (1622-1675) rejected the uterine theory and proposed that the
brain and the spinal cord were the sites of the disease. However, the mind or the mental processes
were not believed necessarily to be located in the brain (Fink, 1996). Thomas Sydenham (16241689) recognized hysteria as a mental disorder. This, combined with Briquet’s (1796-1881)
observation of psychological disturbances in hysteria, set the stage for the conceptualization of
hysteria as a mental disease. Jean-Martin Charcot (1825-1893) recognized that hysteria essentially
involved disturbances of perception and control. Charcot thought that “dynamic or functional
lesions” induced by emotional causes were responsible for these kinds of symptoms (Nijenhuis,
2004). Many other 19th century clinicians in Europe and the United States were confronted by
“hysterical” manifestations that severely tried their sense of what is mental and what is physical,
normal and abnormal. Many founders of modern psychopathology and psychotherapy, including
Jean-Martin Charcot, Alfred Binet and Pierre Janet, among others in France, Josef Breuer and
Sigmund Freud in Austria, and Morton Prince and William James in the United States, studied and
treated patients who presented striking, sometimes shocking, conditions. Some of these symptoms
21
(e.g. blindness, seizures) resembled those of severe somatic pathology, but were not associated with
any detectable anatomical or physiological damage. Other symptoms (e.g. amnesia, different
identities within the same individual) manifested serious cognitive deficits, again without any
medical explanation (Cardeña and Nijenhuis, 2000).
Pierre Janet (1849-1947) was the first to introduce the concept and the name dissociation
(desaggregation mentale) and its connections with traumatic aetiology. The English term merely
implies separation, whereas the French term indicated a forced separation of elements that would
normally aggregate. Janet was a pupil of Charcot and worked in the Salpêtrière clinic in France.
Janet initially elaborated the concept of dissociation in his work on psychological automatism (Van
der Hart and Friedman, 1989). He dealt with psychological phenomena often observable in hysteria,
hypnosis, states of suggestion or possession. Janet postulated that dissociation results from what he
termed la misère psychologique - that is, a pathological, presumably genetic poverty or deficiency
of basic mental energy that enables healthy persons to combine the various mental functions
(sensations, memories, volitions) into a stable, unified psychological structure under the conscious
domination and control of the personal self or ego. If, either spontaneously or as a result of the
emotional expenditure of mental energy in the face of psychological trauma, the quantum of energy
is lowered below a critical point, the binding power of the personal self is seriously impaired, and
the various psychological functions escape from its control (that is, they are dissociated, with all the
potential pathological consequences). Psychological systems that fail to integrate with the larger
personality become self-organized into a smaller and generally more rudimentary part of the
personality, which as well as having its own sense of self, can exert influence over the individual’s
behaviour (Dorahy and Van der Hart, 2006; Van der Hart and Friedman, 1989; Van der Hart and
Horst, 1989).
After the sudden death of Charcot, many of his ideas of about the presumably physical nature of
hypnosis were discarded in favour of the view that hypnosis was a psychological phenomenon
based purely on suggestion. Janet was soon the only one in the Salpêtriere using hypnosis in his
research and clinical work, and published many studies on hysteria. Babinski (1857-1932), formerly
loyal to Charcot, began to regard hysteria as essentially the result of suggestion, and even a form of
malingering; a disorder able to disappear entirely by the influence of persuasion. Dejerine (18491917), the next director of the Salpêtriere clinic, regarded hypnosis as morally reprehensible, and
eventually Janet had to leave the Salpêtriere. After that he lectured in North and South America and
received an honorary doctorate at Harvard in 1936 (Van der Hart and Friedman, 1989).
22
Sigmund Freud (1856-1939), like Janet, based his initial psychological explanation of the
aetiology of hysteria on the occurrence of a dissociative disappearance from the consciousness of
mental contents that, although now unconscious, can influence the form and distribution of
hysterical symptoms. He began to regard somatoform dissociative symptoms as a result of a process
of conversion (i.e. the transformation of unacceptable mental contents into a somatic symptom).
Impressed by the painful quality of traumatic memories, he postulated that the traumatized person
actively dissociated or, in his terminology, “repressed” the painful memories from the conscious
awareness and, by a continuation of this repression, maintained them over time in an unconscious
state to prevent the conscious experiencing of the painful emotions associated with them, and by
converting the painful affects into somatic symptoms symbolically representing the precipitating
trauma (Breuer and Freud, 1955). In other words, whereas Janet adhered to the deficit model of
psychic functioning in which the ego is too weak to maintain its functional integrity, Freud
proposed a conflict model in which a strong ego preserves its normal functions and its emotional
equanimity by protecting itself from psychological pain through the operation of the defensive
mechanism of repression (Nemiah, 2000).
2.1.1. Hypnosis
The use of hypnosis was common among most clinicians studying hysteric manifestations in the
th
19
century, both as a means of investigation and treatment, and in France the concept of
dissociation became linked with hysteria and hypnosis. The psychological phenomena it referred to
were well known to “magnetizers” by the end of the 18th century and the beginning of the 19th
century. They observed patients who talked about themselves in the third person while in a state of
induced or artificial somnambulism, as deep hypnosis was then known (Van der Hart and Horst,
1989). One of the early magnetizers, Marquis de Puységur, began to refer to hypnotic states as
artificial somnambulism, because of their resemblance to natural sleepwalking. The word
“somnambulism” was expanded to include any kind of activity pursued while in a dissociated
condition. Hypnosis was “artificial somnambulism”, dissociation induced by a therapist for
experimental or therapeutic purposes, a deliberate imitation of hysteria. Multiple personality was a
somnambulistic condition in which two or more dissociated states are strikingly distinct in
behaviour, mood and intention, and in which one or several of the states are amnesic for one or for
others. Pierre Janet was the first to describe somnambulism as a phenomenon whereby two or more
states of consciousness are dissociated by the cleft of amnesia and seem to operate independently of
one another (Haule, 1986). Patients suffering from the 19th century diagnosis of hysteria were, as a
23
rule, highly “suggestible”. In more recent studies, associations between hypnotizability and
dissociative experiences or disorders have been found (A÷argün et al., 1998; Carlson and Putnam,
1989; Frischholz et al., 1992).
2.1.2. Towards the 21st century
Regardless of the differences between their theoretical models of psychological functioning, both
Freud and Janet initially emphasized the importance of traumatic events and their painful memory
traces as a central factor in the formation of dissociative symptoms. Freud later abandoned the
trauma aetiology of dissociation and shifted his attention from painful memories of actual traumatic
events to the existence of painful, developmentally-derived inner sexual and hostile drives and
fantasies as the source of psychological conflict (Blizard, 2003).
Later, the British psychologist and psychiatrist Charles Myers, with his work on World War I
soldiers, introduced the concept of psychic traumatization in war (Myers 1916a, b). He described a
basic form of structural dissociation in acutely traumatized (“shell-shocked”) World War I combat
soldiers (Van der Hart et al., 2000). Myers demonstrated that dissociation involved the co-existence
of and alternations between a so-called Apparently Normal (ANP) and an Emotional
Part (EP) of the personality. Survivors, as ANP, were fixated in trying to go on with normal life,
and were thus directed by action systems of daily life, while avoiding the traumatic memories. As
EP, they were in the action system (e.g. defence) or subsystems (e.g. hypervigilance, flight, fight)
that were activated at the time of the traumatization. This theory and the work of Pierre Janet
formed the basis of a modern dissociation theory: the Theory of Structural Dissociation (Van der
Hart et al., 2006).
Interest in dissociation and psychic traumatization began to emerge again with studies on
Vietnam War veterans and the recognition of post-traumatic stress disorder (PTSD). At the same
time, in the 1970s and 1980s, the association between dissociative disorders and childhood physical
or sexual abuse became an important issue in the study of dissociation. Ernest R. Hilgard continued
Pierre Janet’s work and tradition. In the “neodissociation” theory, Hilgard postulated that the
secondary dissociated consciousness is characterized by the hidden observer, which has the quality
of a central stream of consciousness in which information converges from many secondary streams
or secondary personalities (Hilgard, 1974, 1984).
In Finland, psychiatrist Reima Kampman was one of the pioneers in the study of hypnosis and
dissociation in the 1970s. He published his doctoral dissociation on hypnotically induced multiple
24
personality (Kampman, 1973), but consided today the weight of evidence of his work was
moderate.
Today, the importance of childhood physical and sexual abuse (Chu and Dill, 1990; Van der
Kolk et al., 1996), family dysfunction (Draijer and Langeland, 1999), parental verbal aggression
and especially multiple forms of childhood maltreatment (Teicher et al., 2006) in the development
of dissociative symptoms or disorders has been recognized and accepted. However, there still exists
much debate, especially in the United States, on the validity of traumatic memories, and on
dissociative amnesia for the traumatic memories (Chu and Bowman, 2000; Chu et al., 1999;
McNally, 2007; McNally et al., 2005). In 1992 the False Memory Syndrome Foundation was
founded. This group stated that a substantial number of professionals and therapists in the field
were utilizing suggestive and unproven techniques that resulted in vulerable patients developing
false memories of childhood abuse (Chu and Bowman, 2000). Today, the development of new
models and theories of traumatization and dissociation include more sophisticated evaluations of
reports of abuse, better differential diagnosis, and treatment focused on helping patients form a
credible sense of their personal history rather than simply uncovering more trauma (Chu and
Bowman, 2000). In recent years, individual reactions to trauma due to war and terrorist attacks have
again become a target for research.
2.2. Definitions of dissociation
A wide range of definitions for dissociation have been proposed by researchers and clinicians.
While they might differ in detail, what is common in all definitions is a reference to the lack of
usually expected connections between mental content. Dissociative experiences are characterized
by a compartmentalization of consciousness. That is, certain mental events that would ordinarily be
expected to be processed together (e.g. thoughts, emotions, motor activity, sensations, memories
and sense of identity) are functionally isolated from one another and, in some cases, rendered
inaccessible to consciousness and/or voluntary recall (Steinberg, 1994).
According to the Diagnostic Manual for Mental Disorders, Fourth edition, Text Revision (APA,
2000), the essential feature of dissociation is “a disruption of the normal integrative functions of
consciousness, memory, identity, and perception of the environment.” Nemiah (1991) defines
dissociation as “the exclusion from consciousness and the inaccessibility of voluntary recall of
mental events, singly or in clusters, of varying degrees of complexity, such as memories, sensations,
feelings, fantasies and attitudes.”
25
Somatoform dissociation denotes phenomena that are manifestations of a lack of integration of
somatoform experiences, reactions, and functions (Nijenhuis et al., 1996). Both descriptors,
psychological dissociation and somatoform dissociation, refer to the ways in which dissociative
symptoms may be manifested, not to their presumed cause. Somatoform dissociation designates
dissociative symptoms that phenomenologically involve the body, and psychological dissociative
symptoms are those that phenomenologically involve psychological variables. The descriptor
‘somatoform’ indicates that the physical symptoms resemble, but cannot be explained by, a medical
symptom or the direct effects of a substance (Nijenhuis, 2000). Psychological dissociation has also
been defined by the term psychoform dissociation (Van der Hart et al., 2006).
Definitions of dissociation also differ according to whether states or traits are being discussed.
The notion of a dissociative state implies that dissociation can be an episodic phenomenon. State
dissociation is experienced by some people some of the time, is time limited and presumably
situation triggered. A dissociative trait refers to dissociation as a common personality feature which,
like all personality features, is expressed to a greater or lesser degree in each individual (Nijenhuis,
2004).
Dissociation can be understood as a psychic defence mechanism, or as a symptom (or a cluster of
symptoms) significantly manifested in various psychiatric disorders or as a distinct disorder.
2.2.1. Dissociation as a defence mechanism
One of the main strivings of the human psychological system is to maintain organisation and
avoid disintegration. Defences are those mental and behavioural activities that protect the system
from threats to this organisation such as overwhelming, conflicting and intolerable emotions.
Simply stated, the purpose of a defence is to protect individuals by helping them to avoid or manage
these threats (McWilliams, 1994).
Central to the concept of the adaptive function(s) of dissociation is the idea that dissociative
phenomena exist on a continuum and become maladaptive only when they exceed certain limits in
intensity or frequency, or occur in an inappropriate context. Dissociation provides a capacity to
adaptively detach from disturbing emotional states, the milder manifestations being common and
highly functional, and more severe variants less common and typically less functional (Bowins,
2004). Dissociation is seen as a normal process that is initially used defensively by an individual to
handle traumatic and overwhelming experiences, and dissociative experiences are found to be risk
factors for dissociative pathology (Putnam, 1989). At the ‘normal’ end of the continuum are
commonly reported, transient and non-disruptive dissociative experiences such as becoming
26
absorbed in an activity, day-dreaming and performing well-learned actions without conscious
awareness. At the pathological end of the continuum are rarer but more pervasive and lifedisrupting experiences such as chronic depersonalization and identity alteration (Putnam, 1989).
There is a difference between dissociation, the psychodynamic notion of repression and the
conscious act of suppression. Repression refers to the sequestering of unacceptable, conflicting or
intolerable material from consciousness. Repressed psychic material cannot make itself known
directly; its existence is inferred through slips of the tongue, dreams and other symbolic
phenomena. The difference between repression and dissociation can be seen in Hilgard’s (1974)
image of repressed material as existing below a horizontal barrier, above which lies consciousness,
and dissociated material as being separated from consciousness by vertical barriers. Suppression
can be distinguished from both repression and dissociation in that it involves a conscious effort to
‘not think about’ something. The person engaged in suppression does not have amnesia for the
suppressed material, the material does not reside sub- or unconsciously and the suppressed material
can be readily accessed.
It has been suggested that trauma-induced dissociative reactions resemble the defensive reactions
of animals (freezing, aggression) (Nijenhuis et al., 1998b). Nijenhuis and coworkers have proposed
that as a result of an evolutionary mechanism common to many species, there may be a similarity
between distinct animal defensive reaction patterns and certain somatoform dissociative symptoms
of traumatized dissociative disorder patients, such as analgesia, anaesthesia and motor inhibitions
(Nijenhuis, 2004). It has been suggested that among a wide range of potentially traumatizing events,
somatoform dissociative symptoms would most strongly be associated with a bodily threat and a
threat to the life of an individual (Nijenhuis et al., 2001, 2004; Waller et al., 2000).
2.2.2. Cognitive theory
Cognitive theory proposes a cognitive organization that operates during times of perceived or
actual threat from an internal and/or external source in individuals with dissociative pathology. This
is called a dissociative processing style, which serves as a threat-monitoring system (Dorahy, 2006).
Whilst activation of the dissociative processing style has the potential for adaptive and protective
functions, it also heightens the likelihood of experiencing dissociative symptoms and dissociation
itself. It is characterized by a shift from selective attention processing to multiple streams of
information processing, weakened cognitive inhibitory functioning that allows these streams to be
operational and the directing of awareness towards some and away from other information streams.
Dissociation is understood here as a failure to integrate encoded representations (e.g. environmental
27
stimuli) and internal features (e.g. affects, cognitions) from multiple input streams that, without the
process of dissociation, would be put together (Dorahy, 2006). The findings of DePrince and Freyd
(2004) have also suggested that in an effort to avoid threat stimuli, divided attention may serve a
protective function by reducing the likelihood that such stimuli are encoded. Somewhat
controversial suggestions have also been proposed: nonpathological dissociation might reflect a
constitutionally determined cognitive style rather than a pathological trait acquired through the
experience of adverse life events (De Ruiter et al., 2006). In behavioural and neural studies, highly
dissociative individuals were characterized by heightened levels of attention, working memory and
episodic memory. Nevertheless, the authors suggest that individuals with high dissociative abilities
might be prone to develop dissociative disorders when exposed to traumatic experiences,
whereas individuals without dissociative tendencies might develop depressive symptoms, PTSD,
borderline personality or psychotic features (De Ruiter et al., 2006).
2.2.3. Dissociation as a symptom
Dissociative symptoms can be categorized in many ways. In the current scientific literature they
are divided into psychological (or psychoform) and somatoform dissociative symptoms. Core
psychological dissociative symptoms include amnesia, depersonalization, derealization, identity
confusion and identity fragmentation (Bernstein and Putnam, 1986; Steinberg, 1994). The
somatoform dissociative symptoms include a mixture of conversion and somatoform symptoms
(Nijenhuis et al., 1999).
2.2.3.1. Psychological dissociative symptoms
Dissociative amnesia is “the absence from memory of a specific and significant period of time”
(Steinberg, 1994). It is viewed as a functional amnesia as it occurs in the absence of any known
organic cause and is distinguished from other forms of amnesia such as childhood amnesia in that it
does not reflect normal psychological development. Individuals experiencing dissociative amnesia
typically retain the ability to learn and recall new information; memory loss is restricted to a
circumscribed period of time or category of events within the individual’s life, usually of a
traumatic or stressful nature (APA, 2000). Amnesia may be reversible (Bremner et al., 1996; Van
der Hart et al., 2005).
28
Depersonalization refers to a feeling of detachment or estrangement from one’s self
and
includes “a sensation of being an outside observer of one’s body” and “feeling like an automaton or
as if one is living in a dream” (APA, 1994). In clinical samples, chronic depersonalisation is the
third most frequently reported symptom after depression and anxiety (Gershuny and Thayer, 1999).
Derealization refers to “an alteration in the perception of one’s surroundings so that a sense of
reality of the external world is lost” (APA, 1994). Individuals experiencing derealization may feel
as though they have lost contact with external reality; that their home, workplace, friends or
relatives are
unfamiliar
or
strange (Steinberg et
al., 1993). Transient states of
depersonalisation and derealization are common and spontaneous, especially under conditions of
fatigue, anxiety and danger (Butler et al., 1996).
Identity confusion refers to the subjective feelings of uncertainty or conflict regarding one’s
personal identity. Individuals with dissociative symptoms often express confusion as to who they
really are. They experience conflicting wishes and opinions (Steinberg et al., 1993).
In identity alteration, different ‘identities’ or ‘personality states’ take over the control of the
personality. This is also the core diagnostic feature of dissociative identity disorder (DID), where
dissociative parts of the personality (at least two alter personalities or personality states) can be
detected, and switching observed (APA, 1994). The alter personality has been defined as “an entity
with a firm, persistent, and well-founded sense of self and a characteristic and consistent pattern of
behaviour and feelings in response to given stimuli. It must have a range of functions, a range of
emotional responses, and a significant life history (of its own existence)” (Kluft, 1984).
Alternatively, the DSM-IV states that “each personality state may be experienced as if it has a
distinct personal history, self-image, and identity, including a separate name” (APA, 1994).
2.2.3.2. Somatoform dissociative symptoms
Dissociation also manifests in disturbances of sensations, movement and other bodily functions
(Nijenhuis et al., 1999). Nijenhuis and coworkers have labelled these disruptions as ‘somatoform
dissociation’ (Nijenhuis et al., 1996). Somatoform dissociative symptoms include different kinds of
functional or perceptual losses (sensation, pain, motor action), and/or intrusion symptoms of bodily
sensations and movements (e.g. tics), and pseudoseizures (Nijenhuis et al., 1998a). In the
development of the Somatoform Dissociation Questionnaire (SDQ-20), 20 items were selected from
75 items that best reflected instances of somatoform dissociation (Nijenhuis et al., 1996). From
these 20 items, the five that could best characterize ‘hysteria’ according to Janet were further
selected to form a short screening instrument, the SDQ-5. These include insensitivity to pain
29
(analgesia), the sensation of disappearance of the body or parts of it (kinaesthetic anaesthesia),
retraction of the visual field (visual anaesthesia), and difficulty in speaking or the inability to speak
(motor disturbance), as well as a specific symptom, i.e. pain while urinating (Nijenhuis et al., 1997).
In a Finnish non-clinical sample a clear link was found between visual distorsions (micropsia,
macropsia, metamorphopsia and teleopsia) and dissociation (Lipsanen et al., 1999).
2.2.3.3. Dissociative symptoms according to the Structural Dissociation Theory
In their book “The Haunted Self” (Van der Hart et. al, 2006), three leading researchers on
dissociation, Onno Van der Hart, Ellert Nijenhuis and Kathy Steel, have proposed their new theory
of structural dissociation of the personality in combination with a Janetian psychology of action.
According to the theory of structural dissociation, the key concept of understanding traumatization
is dissociation. Based on this theory they have also developed a model of phase-oriented treatment
that focuses on the identification and treatment of structural dissociation and related maladaptive
mental and behavioural actions.
Janet’s clinical observations suggested that hysteria involves psychological and somatoform
functions and reactions. In his view, mind and body were inseparable; thus, his classification of
dissociative symptoms does not follow a body-mind distinction. He divided dissociative symptoms
into permanent symptoms, “mental stigmata”, which mark all cases of hysteria, and “mental
accidents”, which are incidental and depend on each case. “Mental stigmata” include functional
losses such as the partial or complete loss of knowledge (amnesia), loss of sensations including
tactile sensations, kinaesthesia, smell, taste, hearing, vision and pain sensitivity (analgesia), and loss
of motor control (inability to move or speak). In the recent literature they have been referred to as
negative dissociative symptoms. “Mental accidents” represent positive symptoms because they
involve additions, i.e. mental phenomena, that should have been integrated in the personality, but
because of integrative failure become dissociated material that intrudes into the consciousness at
times. Examples include re-experiencing more or less complete traumatic memories and
manifestations of dissociative personality states (Nijenhuis, 2000). The phenomenological
categorization of dissociative symptoms according to the Structural Dissociation Theory is
presented in Table 1.
Based on the work of Charles Myers with (“shell-shocked”) World War I combat soldiers (Van
der Hart et al., 2000), the authors describe the division of the personality in terms of dissociative
parts of the personality. This choice of term emphasizes the fact that dissociative parts of the
personality together constitute one whole, yet are self-conscious, have at least a rudimentary sense
30
of self, and are generally more complex than a single psychobiological state (Van der Hart et al.,
2006).
In traumatized individuals the simplest dissociative division of the personality is primary
structural dissociation. It consists of a single apparently normal part of the personality (ANP) and a
single emotional part of the personality (EP). This division of the personality seems to evolve most
often in relation to a single traumatizing event, and the primary structural dissociation characterizes
simple trauma-related disorders, such as simple forms of post-traumatic stress disorders (PTSD) or
conversion disorders. However, the dissociative organization of the personality can be much more
complex, particularly in those who have experienced chronic childhood abuse and neglect (Van der
Hart et al., 2006). In general, more severe forms of traumatization involve greater levels of
dissociative symptoms (Chu et al., 1999; Draijer and Langeland, 1999; Teicher et al., 2006).
Adults may develop forms of complex trauma-related structural dissociation when their
traumatization is prolonged and repeated. Such adult trauma includes war, torture and internment in
concentration camps. However, it may be that most adults who develop secondary structural
dissociation do so because they have already been traumatized in childhood (Donovan et al., 1996).
In secondary structural dissociation of the personality, chronically traumatized individuals may
experience further division of their personality, resulting in a single ANP and more than one EP.
These EPs may be more elaborated than those in primary structural dissociation, and take not only
physical defensive characteristics, but also contain rigid and maladaptive mental defensive action
tendencies (Van der Hart et al., 2006).
Tertiary structural dissociation involves not only more than one EP, but also more than one ANP.
It is the most complex form of structural dissociation and is typical of many cases of dissociative
identity disorder (DID). In such cases, the action systems of daily life, such as exploration,
attachment and care-taking, which are found in a single ANP in primary and secondary structural
dissociation, are now divided among several ANPs. DID patients may continue to develop
additional ANPs because daily life may be overwhelming due to a difficult environment, internal
chaos from conflicts among dissociative parts of the personality, and chronic reactivation of
traumatic memories. The more complex the structural dissociation is, the more likely one or several
parts of the personality are to emancipate and act autonomously (Van der Hart et al., 2006).
31
Table 1. The phenomenological categorization of dissociative symptoms (Van der Hart et al.,
2006).
Psychoform dissociative symptoms
Somatoform dissociative symptoms
Negative dissociative
Loss of memory: dissociative amnesia
Loss of sensations: anaesthesia
symptoms
Depersonalization involving a division
(all sensory modalities)
between experiencing and observing
Loss of pain sensitivity: analgesia
part of the personality
Loss of motor actions, i.e. loss of the
Loss of affect: emotional anaesthesia
ability to move (e.g. catalepsy), speak,
Loss of character traits
swallow, etc.
Positive dissociative
Psychoform intrusion symptoms
Somatoform intrusion symptoms,
symptoms
(Schneiderian symptoms), e.g.
e.g. “made” sensations and body
hearing voices, “made” emotions,
movements (e.g. tics)
thoughts, and ideas
Pseudoseizures
Psychoform aspects of re-experiencing
Somatoform aspects of
traumatizing events, e.g., particular
re-experiencing traumatizing events,
visual and auditory perceptions, affects,
e.g., particular trauma-related
and ideas
sensations and body movements
Psychoform aspects of alterations between
Somatoform aspects of alterations
dissociative parts of the personality
between dissociative parts of the
personality
Psychoform aspects of dissociative psychosis,
Somatoform aspects of dissociative
i.e., a disorder involving a relatively
psychosis
long-term activation of a psychotic
dissociative part
2.2.4. Dimensional or categorical construct?
The dimensional model of dissociation proposes that dissociation represents a continuous
construct, and it is experienced to a lesser or greater degree by all people. The hypothesis that
dissociation is a normal process that is initially used defensively by an individual to handle
traumatic experiences and evolves over time into a maladaptive or pathological process has been
expressed in a variety of forms over the years, for example by Morton Prince at the beginning in the
32
20th century (Putnam 1989). Ernest Hilgard (1974, 1984), with his neodissociative theory of the
mind, was one of the most instrumental modern figures advocating the concept of a continuum of
dissociation from the normal to the pathological (Putnam, 1989). Hilgard (1984) characterized
hypnosis as a state which produces a certain readiness for dissociative experiences. Thus, evidence
to support the idea of a dissociative continuum comes from research on the distribution of hypnotic
susceptibility in either normal or patient populations. Patients with dissociation and post-traumatic
disorders have most frequently been found to be highly hypnotizable, whereas those with affective
or anxiety disorders, or schizophrenia were relatively less hypnotizable (Carlson and Putnam, 1989;
Spiegel et al., 1988).
The development of the Dissociative Experiences Scale (DES) (Bernstein and Putnam, 1986)
was consistent with the dimensional model of dissociation. The DES assesses a person’s standing
on one or more dissociative dimensions. Most studies using the DES have relied on statistical
procedures for dimensional reduction (Akûyz et al., 1999; Frischholz et al., 1992; Ross et al., 1990).
The DES was explicitly constructed to be a stable trait measure of dissociative experiences (Carlson
and Putnam, 1993).
Later, it was observed that dissociative symptoms are dichotomously distributed, and the
frequency and type of dissociative experiences reported by members of certain diagnostic groups
have suggested “the existence of two or more dissociation types” (Putnam et al., 1996). This finding
was investigated and confirmed by Waller and coworkers (Waller at al., 1996; Waller and Ross,
1997), who made the crucial distinction between items that are pathognomonic of dissociative
disorders and unlikely to be widely endorsed (e.g. “Some people sometimes have the experience of
feeling that other people, objects, and the world around them are not real”) and those that are not
inherently pathological and likely to be widely endorsed by persons in normal as well as clinical
samples (e.g. “Some people find that when they are watching television or a movie they become so
absorbed in the story that they are unaware of other events happening around them”). Waller and
coworkers (1996) suggested that these non-pathological phenomena were manifestations of a
dissociative trait, qualitatively different from the pathological type of dissociation. The 8-item
subscale (DES-T) of pathognomonic items from the DES was developed to identify individuals who
experience pathological dissociation (Waller at al., 1996; Waller and Ross, 1997). Taxometric
methodology and analyses were undertaken with the DES and yielded two distinct classes or
groups; one group comprised members of a taxon who demonstrated pathological dissociation
while the remainders were non-taxon members (Waller et al., 1996). The identification of the
dissociative taxon marks a return to Janet’s original conceptualisation of dissociation as a
33
discontinuity of awareness experienced only by the mentally unwell (Putnam et al., 1996; Waller et
al., 1996).
According to this categorical conceptualization of dissociative phenomena, the distinction
between normal and pathological dissociation represents not only a difference in degree but also a
difference of type (Waller et al., 1996). This conceptualisation explicitly moves the concept of
pathological dissociation away from a dimension or trait model to a discrete or typological
construct and distinguishes pathological forms of dissociation from more “normal” dissociative
states such as day-dreaming. However, there is still controversy over whether dissociation is a
dimensional or categorical construct. Some studies have found support for the taxonic model of
dissociation (Allen et al., 2002; Irwin, 1999), but contradictory results have also been obtained
(Simeon et al., 2003; Watson, 2003).
2.2.5. Dissociation as a disorder and the classification of dissociative disorders
According to the Diagnostic Manual for Mental Disorders, Fourth edition (DSM-IV, American
Psychiatric Association, 1994), the essential feature of dissociation is “a disruption of the normal
integrative functions of consciousness, memory, identity, and perception of the environment”. The
classification of somatoform disorders and the former “construct with a hysterical root” remains an
area of division between the DSM-IV and the International Statistical Classification of Diseases and
Related Health Problems (ICD-10, WHO, 1992). The main difference is that what was originally
considered as hysteria has been divided into several independent categories in the current DSM
classification, but in the ICD-10, Conversion and Dissociation categories are inseparable. In the
DSM-IV, the Conversion disorders are within the broader Somatoform disorders category. This
separation in the DSM-IV emphasizes the importance of excluding organic illness (such as
neurological illnesses) when diagnosing these conditions (APA, 1994). The ICD-10 excludes the
depersonalization-derealization disorder from the Dissociative (conversion) disorders on the
grounds that it does not involve a major loss of control over sensation, memory or movement, and is
associated with only minor changes in personal identity (WHO, 1992). The DSM-IV includes a
distinct category for dissociative identity disorder (DID), which is placed (using its former name in
the DSM of multiple personality disorder) in the Other dissociative (conversion) disorders category
in the ICD-10, reflecting controversy over this condition. DSM-IV also requires the presence of at
least three dissociative symptoms for acute stress disorder (ASD), whereas dissociative symptoms
are not a requirement for ASD in the ICD-10. Post-traumatic stress disorder (PTSD) is not
categorized as a dissociative disorder in either the ICD-10 or DSM-IV. These inconsistencies
34
between the DSM-IV and the ICD-10 illustrate the confusion that surrounds the dissociation
concept. A synopsis of the classification of dissociative disorders with comparisons between the
ICD-10 and the DSM-IV-TR (APA, 2000) is presented in Table 2.
There are also differences in the general criteria: the ICD-10 requires convincing associations in
time between the onset of symptoms of dissociative disorders and stressful events, problems, or
needs, but this is not mentioned in the DSM classification. The DSM-IV states that dissociative
symptoms must cause clinically significant distress or impairment in social, occupational or other
important areas of functioning, but the above rule is not included in the ICD-10. With the
development and new formulations of the DSM classification, the dissociative disorders have been
described and categorized differently.
35
Table 2. A synopsis of the classification of dissociative disorders with comparisons between
the ICD-10 and DSM-IV-TR (Lipsanen, 2004).
Code
ICD-10
Code
DSM-IV-TR
F44.0
Dissociative amnesia
300.12
Dissociative amnesia
F44.1
Dissociative fugue
300.13
Dissociative fugue
F44.2
Dissociative stupor
No corresponding category, code as 300.15
Dissociative disorder NOS
F44.3
Trance and possession
No corresponding category, code as 300.15
disorders
Dissociative disorder NOS
F44.4
Dissociative motor
300.11
Conversion disorder with motor symptom
F44.5
Dissociative convulsions
300.11
Conversion disorder with seizures
F44.6
Dissociative anaesthesia
300.11
disorder
or deficit
or convulsions
and sensory loss
F44.7
F44.8
Mixed dissociative
Conversion disorder with seizures
or convulsions
300.11
Conversion disorder with sensory symptom
(conversion) disorders
or deficit
Other dissociative
No corresponding category, code as 300.15
(conversion) disorders
Dissociative disorder NOS
F44.80
Ganser’s syndrome
No corresponding category, code as 300.15
F44.81
Multiple personality
Dissociative disorder NOS
300.14
Dissociative identity disorder
disorder
F44.82
Transient dissociative
No corresponding category, code as 300.15
(conversion) disorders
Dissociative disorder NOS
occurring in childhood
and adolescence
F44.88
Other specified
No corresponding category, code as 300.15
dissociative (conversion)
Dissociative disorder NOS
disorders
F44.9
Dissociative (conversion)
300.15
Dissociative disorder NOS
disorders, unspecified
F48.1
Depersonalization-derealization 300.6
F06.5
Organic dissociative disorder
Depersonalization disorder
disorder
No corresponding category, code as 294.9
Cognitive disorder NOS
36
2.3. Biological factors in dissociative pathology
Smaller hippocampal volumes have been reported in several stress-related psychiatric disorders,
including post-traumatic stress disorder (PTSD) (Bremner et al., 1997, 2003), borderline personality
with early abuse (Driessen et al., 2000), and depression with early abuse (Vythilingham et al.,
2002). Excessive amygdaloid activation has been proposed to play a crucial role in the development
of PTSD (Rauch et al., 1996), and in triggering fight-or-flight responses (Lee et al., 1998).
Although dissociative disorders and especially dissociative identity disorder have been associated
with usually multiple, sustained forms of childhood maltreatment (Anderson et al., 1993; Boon and
Draijer, 1993; Tutkun et al., 1998), there is relatively little knowledge of the biological basis of
dissociative disorders.
Vermetten and coworkers (2006) found that the hippocampal and amygdalar volumes were
smaller in patients with dissociative identity disorder (DID) with comorbid PTSD compared with
healthy controls. The volume reductions were larger in the amygdala than in the hippocampus. It
was suggested that DID would be associated with relatively greater volume reductions in the
amygdala than in the hippocampus.
Apart from single case reports (Mathew et al., 1985, Saxe et al., 1992; Tiihonen et al., 1995),
regional cerebral blood flow (SPECT) has been studied in a sample of 15 patients with dissociative
identity disorder and eight healthy control subjects (ùar et al., 2001). Perfusion differences were
found in orbitofrontal regions bilaterally and the left lateral temporal region among patients with
DID compared with control subjects. Among patients with DID, different cognitive and emotional
characteristics of alter personality states were also observed in order to screen state-dependent
perfusion changes, but no such evidence was found. It was suggested that the observed perfusion
pattern in the DID patients was a trait characteristic rather than a state dependent one (ùar et al.,
2001).
Flor-Henry and coworkers (1990) documented two cases of multiple personality disorder with
left hemisphere activation in EEG analysis and bilateral frontal and left temporal dysfunction in
neurophysiological test batteries. These results were interpreted as resulting from the disruption of
intrahemispheric inhibition (Flor-Henry et al., 1990). It has also been suggested that some
personality shifts may be associated with activation and transition to the right hemisphere dominant
mode (Teicher et al., 2002). In a Finnish non-clinical sample of 297 adults, in addition to female sex
and younger age, non-right handedness accounted for 24% of the total variance of the DES. It was
hypothesized that non-right handedness was a predisposing factor for dissociative episodes,
especially in female subjects (Lipsanen et al., 2000).
37
2.4. Assessment of dissociative symptoms with questionnaires
There are several psychometric measures to quantify dissociative symptoms among individuals.
The purpose of the development of these measures has been to help identify patients with
dissociative psychopathology by screening with self-report questionnaires, and as a research tool to
provide a means to quantify dissociative experiences and symptoms.
2.4.1. The Dissociative Experiences Scale (DES)
The most commonly used instrument to assess dissociation is the Dissociative Experiences Scale
(DES) (Bernstein and Putnam, 1986). It is a 28-item self-report questionnaire to measure
psychological aspects of dissociation. The DES is based on the concept of dissociation as a
continuum from minor dissociations of everyday life to major forms psychopathology (Bernstein
and Putnam, 1986). The DES was developed to be a trait measure of dissociation and it inquires
about the frequency of dissociative experiences in daily life. It has been shown to have good
internal reliability, strong convergent validity with other measures of dissociation across 26 studies,
and discriminant validity in distinguishing dissociative disorders from other diagnostic groups (Van
Ijzendoorn and Schuengel, 1996). The DES has a four-week test-retest stability of 0.93 (Frischholz
et al., 1990).
The first version of the DES utilized a visual analogy scale consisting of a 100-mm line
numerically anchored at endpoints but with no divisions. The subject was instructed to indicate his
or her response to each question by making a slash across the 100-mm line at the appropriate place.
The response was scored by using a ruler to measure the distance in millimetres from the zero point
to the slash mark (Bernstein and Putnam, 1986). In the second version (DES II), subjects were
asked to indicate with a circle on a visual analogy scale what percentage (0%-100%) of the time
within ten percentage points they experienced dissociative symptoms. The individual’s total score
was the mean of the 28 items, and higher scores indicated greater levels of dissociation. The DES II
has some advantages compared with the DES I, as it is easier to score and response choices are
clearer (Ellason et al., 1991). The second version has almost entirely replaced the first version in
research and clinical settings, and was used in this study.
The DES has been divided in three factors or subscales (Carlson and Putnam, 1993) that each
measure different aspects of dissociative experiences. The absorption and imaginative involvement
factor (DES-ABS) has mostly been considered to reflect the nonpathological aspects of
38
dissociation. The amnestic (DES-AMN) and depersonalization-derealization (DES-DD) factors
have consisted more of questions measuring pathological dissociation.
A Dissociative Experiences Scale Taxon (DES-T) with eight items (numbers 3, 5, 7, 8, 12, 13,
22, and 27) from the DES has been developed to more clearly distinguish the pathological
component of dissociation (Waller et al., 1996; Waller and Ross, 1997). This scale measures
identity alteration, depersonalization, derealization, discontinuation of awareness, dissociative
amnesia, and auditory hallucinations. The typological model suggests that an individual either
belongs to a pathological dissociative taxon or not, and that nonpathological dissociation is a
dimensional phenomenon. The taxon membership probabilities can be calculated with a statistical
program on the basis of the weights for each DES-T item score (Waller and Ross, 1997 p. 510). It is
also possible to calculate the unweighted mean of the DES-T items, and choose different cut-off
scores to measure significant levels of pathological dissociation (Ross et al., 2002; Waller and Ross,
1997).
Various cut-off scores of the DES have been used to identify those who might have a
dissociative disorder or a disorder with a considerable dissociative component. Cut-off scores of 1530 have been suggested to distinguish subjects with significant dissociative symptomatology
(Draijer and Boon, 1993; Ross et al., 2002; Steinberg et al., 1991; Waller at al., 2001; Waller and
Ross, 1997). The DES is not, however, a diagnostic tool. To obtain a reliable diagnosis, subjects
with high DES scores should be interviewed either using the complete DES questionnaire or
structured clinical interviews for dissociative disorders such as for example the Structured Clinical
Interview for DSM-III-R Dissociative Disorders (SCID-D) (Steinberg et al., 1991, 1993) or the
Dissociative Disorders Interview Schedule (DDIS) (Ross et al., 1989; Ross and Ellason 2005).
2.4.2. The Somatoform Dissociation Questionnaire (SDQ-20)
The Somatoform Dissociation Questionnaire (SDQ-20) was developed in 1996 by Ellert
Nijenhuis and his coworkers to assess the somatoform components of dissociation (Nijenhuis et al.,
1996). The SDQ-20 is a self-report questionnaire of 20 items. An individual is asked to identify to
what extent each statement is applicable to him or her. Items include such statements as “My body,
or part of it, feels numb”, “I can’t swallow, or only with great effort”, and “My body, or part of it, is
insensitive to pain”. The score corresponding to the response to each statement ranges from 1 to 5,
and the total score from 20 to 100. The SDQ-20 has excellent internal consistency, strong
convergent validity with the DIS-Q and the DES (Nijenhuis et al., 1996, 1999) and construct
validity as measured by its correlation with reported trauma (Nijenhuis et al., 1998c).
39
The SDQ-20 has not previously been used in general population samples, but it has been used
with dissociative disorder patients, patients from other different diagnostic categories and nonclinical participants (El-Hage et al., 2002; Espirito Santo and Pio-Abreu, 2007; Nijenhuis, 2000; ùar
et al., 2000). With a cut-off score of 30, patients with DSM-IV dissociative disorders were
discriminated from psychiatric patients with other disorders with a sensitivity of 0.90 and a
specificity of 0.75 (ùar et al., 2000). A recent study compared dissociative disorder patients with
patients from other diagnosis groups, where a cut-off score of 35 was found optimal for differential
diagnosis in a clinical sample (Espirito Santo and Pio-Abreu, 2007).
A brief five-item screening version of the SDQ-20 has been developed by the same authors, the
SDQ-5 (Nijenhuis et al., 1997). The five items include insensitivity to pain (analgesia), the
sensation of disappearance of the body or parts of it (kinesthetic anaesthesia), retraction of the
visual field (visual anaesthesia), difficulty in speaking or the inability to speak (motor disturbance),
and pain while urinating. However, the SDQ-5 has been shown to be more vulnerable to cultural
differences than the original SDQ-20 (ùar et al., 2000).
2.4.3. Other measures
Other self-administrated scales to measure dissociative experiences have been developed, but
their use in clinical or non-clinical samples has been more infrequent than the use of the DES or the
SDQ-20. Both the Multidimensional Inventory of dissociation (MID) and the Dissociation
Questionnaire (DIS-Q) include considerably more items compared with the DES or the SDQ-20,
and are thus not as suitable for large epidemiological surveys.
2.4.3.1. The Dissociation Questionnaire (DIS-Q)
The Dissociation Questionnaire (DIS-Q) was the first European clinical scale to assess
dissociation (Vanderlinden et al., 1991). It is a 63-item, self-report instrument with a five-point
Likert format. Its four scales (i.e. identity confusion and fragmentation, loss of control, amnesia,
absorption) have good internal consistency and a three-to-four-week test-retest stability. The DIS-Q
has discriminated dissociative disorder patients from normal adults and other psychiatric patients
(Vanderlinden et al., 1993).
40
2.4.3.2. The Adolescent Dissociative Experiences Scale (A-DES)
The Adolescent Dissociative Experiences Scale (A-DES) is a questionnaire for screening
dissociation during adolescence. It is a 30-item self-report questionnaire with an 11-point scale
ranging from “never” to “always” (Armstrong et al., 1997). It was used in a Finnish sample of 4019
adolescents, where a high level of dissociation was associated with an age of 15 or less, daily
smoking, frequent use of alcohol, abuse of legal drugs, cannabis use, social isolation and poor
performance in mathematics (Tolmunen et al., 2007).
2.4.3.3. The Multidimensional Inventory of dissociation (MID)
The MID is a 218-item, self-administrated multiscale instrument that comprehensively assesses
the phenomenological domain of pathological dissociation and diagnoses dissociative disorders. It
was designed for clinical research and for diagnostic assessment of patients who present with a
mixture of dissociative, post-traumatic and borderline symptoms. The MID has demonstrated
internal reliability, temporal stability, convergent validity, discriminant validity and construct
validity (Dell, 2006a). The MID has been used in a study with dissociative identity disorder patients
to comprehensively evaluate all dissociative symptom modalities (Dell, 2006b).
2.5. Dissociation in the general and non-clinical population
2.5.1. Prevalence of dissociative symptoms in general and non-clinical populations
2.5.1.1. Prevalence of psychological dissociation
The majority of non-clinical or general population studies have used the DES as a measurement
scale for dissociation (Akyüz et al., 1999, 2005; Lipsanen et al., 2003; Putnam et al., 1996; Ross et
al., 1990; Xiao et al., 2006a), or a modified version of the DES (Mulder et al., 1998). In two studies,
pathological dissociation was measured with the eight-item DES-Taxon (Seedat et al., 2003; Spitzer
et al., 2006). The DIS-Q has been used in one general population study (Vanderlinden et al., 1991).
A summary of these previous studies is presented in Table 3.
41
Studies on general populations have demonstrated that dissociative experiences are quite
common, and their prevalence has ranged from 1.0% to 12.8% (Akyüz et al., 1999, Ross et al.,
1990), depending on the scale used or on the cut-off point selected to indicate a high level of
dissociation. Among a general population sample of Turkish females, 15.9% of the participants
scored over 20 in the DES (Akyüz et al., 2005). Other studies (Putnam et al., 1996; Waller and
Ross, 1997) have questioned the highest estimates of the prevalence of dissociative disorders in the
general population. Instead of considering dissociation as a continuum from normal to pathological,
a typological model has been developed (Waller and Ross, 1997). The prevalence of pathological
dissociation (DES-T •20) has been found to be 4.4% in the North American general population
(Seedat et al., 2003). The prevalence of DES-taxon membership was reported as 3.3% in the
Canadian general population (Waller and Ross, 1997), but it was much lower in German (0.3%;
Spitzer et al., 2006) and Chinese (0.5%; Xiao et al., 2006a) non-clinical population samples.
The lowest mean DES score of 2.6 (SD 4.3) has been detected among a Chinese non-clinical
population sample of factory workers (Xiao et al., 2006a). In other studies the mean DES score has
ranged from 6.7 (SD 6.1) in a Turkish general population (Akyüz et al., 1999) to 10.8 (SD 10.2) in a
Canadian general population sample (Ross et al., 1990). Among the Turkish female general
population the mean DES score was 11.8 (SD 10.2) (Akyüz et al., 2005).
2.5.1.2. Prevalence of somatoform dissociation
Until now, no studies on the prevalence of somatoform dissociation in the general population have
been published. There have been only two studies on non-clinical samples in which the mean SDQ20 score has been reported. One of these was carried out on a Turkish non-clinical population (ùar
et al., 2000), including 175 participants aged 18-64 years (mean age 30.3 years [SD 9.4]). The mean
SDQ-20 score of this sample was 27.4 (SD 8.2). The other study included a random Dutch sample
of 147 subjects with an age range of 19-77 years, and also a student sample of 73 participants aged
17 to 29 years (mean age 21.8 years [SD 2.3]). The mean SDQ-20 score in these groups was 23.2
(SD 5.0) and 24.4 (SD 4.4), respectively (Näring and Nijenhuis, 2005).
42
Table 3. Prevalence of high dissociation and mean scores from questionnaires on dissociation
in non-clinical population samples.
Author(s)
Sample
year, country
(Age/mean age ± SD)
Female% Questionnaire
for measuring
Prevalence of high
Mean score
dissociation
(± SD)
DES • 20 in 3.8%
6.7 (± 6.1)
dissociation
Akyüz et al.
994 (18-65/34.7 ± 12.9)
1999, Turkey
general population
Lipsanen et al.
924 (18-64/40.1 ± 12.6)
2003, Finland
non-clinical population
Mulder et al.
1028 (18 yrs or more)
1998, New Zealand
general population
47.2
DES
DES • 30 in 1%
60.0
DES
DES
8.4 (± 7.9)
15 items of the DES
occurring often to
always in 6.3%
Putnam et al.
415 (22 yrs or more/40.5)
1996, United States
non-clinical population
DES
DES • 30 in 4.4%
8.3 (± 9.3)
DES
DES • 20 in 12.8%
10.8 (± 10.2)
and Canada
Ross et al.
1055 (20 yrs or more/
1990, Canada
43.2 ± 16.7)
58.3
DES • 30 in 5%
general population
Seedat et al.
1007 (18-65/39.6 ± 13.0)
2003, United States
general population
Spitzer et al.
297 (18-77/39.0 ± 13.2)
2006, Germany
non-clinical population
Vanderlinden et al.
374 (10 yrs or more)
1991, Belgium and
general population
63.3
DES-T
DES-T • 20 in 4.4%
3.5 (± 8.6)
DES-T • 30 in 2%
58.2
DES-T
DES-taxon 0.3%
2.3 (± 4.2)
DIS-Q • 2.5 in 3%
1.7 (± 0.45)
DES-taxon
49.4
DIS-Q
in men
DIS-Q • 3.5 in 1%
Netherlands
1.6 (± 0.37)
in women
Waller and Ross,
1997, Canada
1055 (20 yrs or more/
58.3
DES-taxon
DES-taxon 3.3%
52.0
DES
DES-taxon 0.5%
43.2 ± 16.7)
general population
Xiao et al.
618 (41.7 ± 5.9)
2006, China
non-clinical population
DES-taxon
2.6 (± 4.3)
43
2.5.2. Factors associated with dissociation
2.5.2.1. Sociodemographic factors
2.5.2.1.1. Age
A negative association between age and dissociation scores measured with the DES (Akyüz et
al., 1999; Lipsanen et al., 2000; Ross et al., 1990) or DIS-Q (Vanderlinden et al., 1991) has been
observed in general population samples. Pathological dissociation (DES-T) was also found to be
associated with a younger age (Seedat et al., 2003).
In most studies, age has not influenced the SDQ-20 scores (El-Hage et al., 2002; Nijenhuis,
2000), but in a Turkish mixed sample with clinical and non-clinical participants a weak but
statistically significant correlation was found between the SDQ-20 scores and age (ùar et al., 2000).
2.5.2.1.2. Sex
A meta-analytic study summarizing 19 clinical and non-clinical studies reporting scores for both
men and women concluded that there was no gender difference in dissociative pathology (Van
Ijzendoorn and Schuengel, 1996). In a large German sample of nonclinical and clinical subjects no
gender difference was found in the total DES scores, absorption or pathological dissociation scores.
The only significant difference was in the amnesia subscale of the DES: men scored higher
compared with women (Spitzer et al., 2003). Female subjects scored higher in the DES in a nonclinical Finnish sample (Lipsanen et al., 2000). In one general population study, pathological
dissociation (DES-T) was associated with male gender (Seedat et al., 2003).
No difference has been observed between the Somatoform Dissociation Questionnaire (SDQ-20)
scores of male and female subjects in the majority of clinical and non-clinical samples (Nijenhuis et
al., 1996, 1998a; ùar et al., 2000), but in a French outpatient sample women had higher scores than
men (El-Hage et al., 2002).
2.5.2.1.3. Sosioeconomic and marital status
In the Turkish general population, married subjects had lower DES scores compared with single
subjects (Akyüz et al., 1999), but high dissociation scores have not otherwise generally been
44
associated with marital status or with educational or economic level (Ross et al., 1990).
Pathological dissociation was associated with African-American ethnicity (Seedat et al., 2003).
A negative correlation between high somatoform dissociation, educational level and socioeconomic status was detected in a Turkish sample of clinical and non-clinical participants (ùar et
al., 2000).
2.5.2.2. Adverse Childhood Experiences
The hypothesis that dissociation occurs in response to trauma has a long tradition in psychiatry
from the beginning of the modern research on hysteria and dissociation in the 19th and 20th century
(Van der Hart and Horst, 1989). Dissociation was believed to be used as a means of a defence or an
attempt to adapt to the traumatic experiences; if the extent of the abuse is sufficient, then the
dissociative response regularly becomes relied upon as a defence mechanism and the individual’s
mental processes become intermittently fragmented (Irwin, 1994). The consequences of childhood
sexual and physical abuse and their impact on dissociative symptom formation has been the focus
of dissociation research (Chu and Dill, 1990; Mulder et al., 1998; Van der Kolk et al., 1996), but in
recent years various and multiple forms of childhood maltreatment or adverse childhood
experiences have been studied.
In a large ACE study (Felitti et al., 1998), the categories of adverse childhood experiences were
strongly interrelated and persons with multiple categories of childhood exposure were likely to have
multiple health risk factors in later life. A positive, graded relationship between ACEs and
attempted suicide (Dube et al., 2001), as well as hopelessness (Haatainen et al., 2003), has been
found at the population level. When the association between multiple types of childhood
maltreatment and several outcome measures (including dissociation, depression and anxiety) was
investigated in a non-clinical population of 554 subjects, exposure to multiple forms of
maltreatment was observed to have an effect size that was often greater than the component sum
(Teicher et al., 2006).
In the general population, traumatic experiences have been associated with psychological
dissociation. However, the existence of a direct causal relationship between childhood sexual abuse
and dissociation has been questioned, because of the indirect association with high dissociation: it
was related to both physical abuse and the current mental state (Mulder et al., 1998). Among the
Dutch general population, those subjects with a trauma history had higher scores in the Dissociation
Questionnaire (DIS-Q) compared to subjects with no trauma (Vanderlinden et al., 1993). A recent
study on a non-clinical sample of young adults also showed that combined exposure to parental
45
verbal aggression and witnessing domestic violence was associated with an extraordinarily large
effects size on dissociation, and the association was even stronger than with familiar sexual abuse
(Teicher et al., 2006). Sexual abuse, physical neglect and emotional abuse were associated with a
diagnosis of a dissociative disorder among women in the general population (ùar et al., 2007),
although an earlier study in the same district found no significant associations between high
dissociation and traumatic experiences (Akyüz et al., 1999).
Somatoform dissociation has been shown to be associated with childhood abuse in clinical
samples (Nijenhuis et al., 1998c; Roelofs et al., 2002; Waller et al., 2000). Among various types of
trauma, physical abuse, with an independent contribution of sexual trauma, best predicted
somatoform dissociation. Both psychological and somatoform dissociation were best predicted by
an early onset of reported intense, chronic and multiple traumatization (Nijenhuis et al., 1998c).
Waller and coworkers found that somatoform dissociation was especially associated with physical
abuse and a threat to life from another person (Waller et al., 2000). The relationship between
childhood traumatic experiences and somatoform dissociation has also been examined in two nonclinical samples (Näring and Nijenhuis, 2005).
2.5.2.3. Other psychiatric conditions
2.5.2.3.1. Depression and suicidality
In clinical samples, dissociative disorder patients frequently have comorbid current depression or
a history of major depression (Ellason et al., 1996; Lipsanen et al., 2004a; ùar et al., 2004; Yargic et
al., 1998). A study with depersonalization disorder patients found considerable comorbidity
between depersonalization disorder and depression (Baker et al., 2003). Furthermore, in a study on
chronic pelvic pain patients, dissociative disorders were closely associated with self-reported
anxiety and depression, and with DES scores (Nijenhuis et al., 2003).
At the population level, three studies have examined the association between high dissociation
and comorbid mood disorders/major depression. No statistically significant association was found
between high dissociation (DES>17) and a diagnosis of major depression among the Turkish
general population (Akyüz et al., 1999), but among the general population in New Zealand an
association between dissociative symptoms and mood disorders was detected (Mulder et al., 1998).
In a recent study on a sample of the female Turkish general population, participants with a
dissociative disorder had major depression more frequently than those without a dissociative
disorder (ùar et al., 2007).
46
Patients with dissociative disorders frequently engage in self-destructive behaviour (Low et al.,
2000; Saxe et al., 2002). Many patients who have self-mutilative behaviours report feeling numb
and dead prior to harming themselves. Although self-mutilation is different from actual suicidality
(Pattison and Kahan, 1983), a strong relationship between dissociation, suicide attempts and selfmutilation has been found in a large non-clinical sample (Zoroglu et al., 2003). Among the general
population of female subjects in Turkey, participants with a dissociative disorder more often had a
history of suicide attempts than those without a dissociative disorder (ùar et al., 2007).
In Dutch samples, the SDQ-20 scores were low among patients with mood disorders, especially
among patients with bipolar mood disorder (Nijenhuis, 2000). To my best knowledge, no studies
have yet examined the possible association between high somatoform dissociation and suicidal
ideation.
2.5.2.3.2. Other psychiatric disorders
Dissociative symtoms have been highly correlated with psychopathology (Putnam et al., 1996;
Saxe et al., 1993). The comorbidity of high dissociation, dissociative disorders and other psychiatric
disorders has been examined in three general population studies (Akyüz et al., 1999; Mulder et al.,
1998; ùar et al., 2007) with structured clinical interviewing methods. Akyüz and coworkers found
no association between high dissociation and other diagnostic categories. Post-traumatic stress
disorder (PTSD) and anxiety disorders were associated with high dissociation in New Zealand
(Mulder et al., 1998). Turkish female participants with dissociative disorders had borderline
personality disorder, somatisation disorder, and PTSD more frequently than did participants with a
dissociative disorder (ùar et al., 2007). Only recently, associations between dissociation and
childhood attention-deficit-hyperactivity-disorder (ADHD) have been proposed (Endo et al., 2006;
Matsumoto and Imamura, 2007).
In clinical samples, high somatoform dissociation has been associated with somatoform
disorders (somatisation and conversion disorders) (Espirito Santo and Pio-Abreu, 2007; Nijenhuis,
2000), eating disorders (Nijenhuis, 2000; Waller et al., 2003) and PTSD (Espirito Santo and PioAbreu, 2007). Somatoform dissociation showed particularly strong links with the presence of
bulimic behavioural features and bulimic attitudes (Waller et al., 2003).
47
2.5.2.4. Alexithymia
The association between alexithymia and dissociation has been examined in clinical and nonclinical samples, but no studies have been published on the general population. Previous research
on the relationship between dissociation and alexithymia is summarised in Table 4. This
relationship has been discussed in the theory of psychodynamic medicine (Nemiah 1977, 1991,
2000). The construct of alexithymia was introduced by Sifneos (1973). Alexithymia, meaning ‘lack
of word, mood or emotion’, involves “reductions or incapacities to fantasize, experiences, and
verbalize emotions, and an absence of tendencies to think about one’s emotions” (Sifneos, 1973).
Alexithymia has been characterized by deficits in emotional communication, cognitive
processing and the regulation of emotions (Taylor, 2000). Both dissociation and alexithymia
represent symptoms of somatization (Nemiah, 1991), difficulties with affect regulation (Van der
Kolk et al., 1996) and possible associations with traumatic experiences (Chu and Dill, 1990; Cloitre
et al., 1997; Berenbaum, 1996). Long-lasting alexithymic features have been associated with harsh
discipline and unhappiness of the childhood home, depression at 12 months and major depressive
disorder at 24 months in a two-year follow-up study of patients with major depressive disorder
(Honkalampi et al., 2004).
Significant correlations between dissociation and alexithymia have been found, and the domain
“difficulty identifying feelings” of the TAS-20 has especially been associated with dissociative
symptomatology (Elzinga et al., 2002; Grabe et al., 2000; Irwin and Melvin-Helberg, 1997;
Modestin et al., 2002). However, it has been argued that a depressed mood accounts for the group
differences in scores between the Toronto Alexithymia Scale (TAS-20) and Dissociative
Experiences Scale (DES) (Wise et al., 2000). In two recent studies, despite their mutual
correlations, dissociation and alexithymia have been suggested to be different constructs (Lipsanen
et al., 2004b; Tutkun et al., 2004).
One study has examined the association between alexithymia and both psychoform and
somatoform dissociation (Clayton, 2004). In that study the Bermond Vorst Alexithymia
Questionnaire (BVAQ) was used to assess alexithymia and somatoform dissociation was the
strongest predictor of alexithymia. Somatoform dissociation was directly related to all facets of
alexithymia except for fantasizing.
48
Table 4. The relationship between dissociation and alexithymia in clinical and non-clinical
samples.
Author(s)
Sample (Age/mean age ± SD) Assessment of dissociation
Year, Country
Clayton,
219 non-clinical participants
2004, Australia
Elzinga et al.
Conclusion of the association
and alexithymia
833 undergraduate students
2002, Netherlands 17-30 yrs/20.6 ± 2.8
DES, DES-T, Somatoform
*No association between pathological
Dissociation Questionnaire (SDQ),
dissociation and alexithymia
Bermont Vorst Alexithymia
*Somatoform dissociation was strongly
Questionnaire (BVAQ)
associated with alexithymia
Dissociation Questionnaire DIS-Q, *Positive correlation between dissociation
Toronto Alexithymia Scale
and ‘difficulty identifying feelings’
(TAS-20), BVAQ
*Distinct constructs
Grabe et al.
173 patients and 38
German 44 item version
*Significant correlations between dissociation
2000, Germany
non-clinical participants,
of the Dissociative Experiences
and all dimensions of alexithymia
116 females (38.8 ± 13.2 yrs), Scale (FDS), TAS-20
*Alexithymic characteristics contribute to
95 males (40.2 ± 13.7 yrs
the development of pathological dissociation
Irwin and Melbin- 100 undergraduate students
Questionnaire of Experiences
Helberg
of Dissociation (GED), TAS-20
18-52 yrs/21.9 yrs
1997, Australia
*‘Difficulty identifying feelings’ predicted
dissociative tendencies
*Verbal processing dissociated from
affective processes
Lipsanen et al.
924 non-clinical subjects
DES, TAS-20
*Distinct constructs but correlate significantly
276 medical students
DES, TAS-20
*Alexithymic probands had high DES scores
2004, Finland
Modestin et al.,
2002, Switzerland 24.4 (SD 3.0) yrs
*Positive correlation between dissociation and
‘difficulty identifying and describing feelings’
Tutkun et al.,
154 outpatients
2004, Turkey
Wise et al.
2000, USA
116 outpatients
DES, TAS-20
*Overall effect of dissociation was not significant
TAS-20•61, 34.7 (SD 10.0) yrs
on the TAS-20 total or subscale scores
TAS-20<60, 35.8 (SD 10.4) yrs
*Dissociation is different from alexithymia
DES, TAS-20
*Depressed mood accounted for the group
DES<15, 42.6 (SD 13.4) yrs
differences between the DES and TAS-20
DES•15, 39.7 (SD 12.6) yrs
scores
*Dissociation differs from alexithymia
49
2.5.2.5. Substance use (alcohol and tobacco)
In the alcohol-dependant population, different results have been detected in relation to the level
of dissociative symptomatology (Schäfer et al., 2007). In the general population, associations were
found between substance use and high DES scores (Mulder et al., 1998), as well as harmful alcohol
use and DES-T scores (Seedat et al., 2003).
Exposure to traumatic events and PTSD have been associated with increased smoking (Feldner
et al., 2007; Van der Velden et al., 2007). In a sample of 4019 Finnish adolescents a high level of
dissociation was associated with daily smoking (Tolmunen et al., 2007).
2.5.2.6. Familiality
Contradictory results have been obtained in twin studies, where the relative influences of genetic
and environmental factors on dissociation have been estimated (Becker-Blease et al., 2004; Jang et
al., 1998; Waller and Ross, 1997). Waller and Ross (1997) found no genetic variance, and 45% of
the variance of the DES-T and taxon membership scores was attributable to the shared environment
(i.e. environmental influences that lead to sibling similarity in dissociation), while 55% was
attributable to the non-shared environment (i.e. environmental influences that lead to sibling
differentiation). In contrast to these findings, using taxon membership scores, Jang and coworkers
(1998) obtained a non-shared environment estimate of 52%, but the remaining 48% of the variance
was accounted for by additive genetic influences; the effects of the shared environment were
negligible. A similar pattern was obtained when they examined the non-pathological dissociation
scores. They further estimated that pathological and non-pathological dissociation scores shared
45% of the genetic and 34% of the environmental variance (Jang et al., 1998). The authors
suggested that pathological and non-pathological dissociation scores are influenced by a common
genetic predisposition to dissociate, but are differentiated by environmental factors. Although these
studies had a rather similar sample size of volunteer twins, one included high school students
(Waller and Ross, 1997) and the other one adolescents and adults (Jang et al., 1998). Contrary to
these studies, non-pathological dissociation was examined among child and adolescent twins by
using parents’ and teachers’ ratings of dissociative behaviours (Becker-Blease et al., 2004). The
ratings indicated moderate to substantial amounts of genetic and non-shared environmental variance
and negligible shared environmental variance. Longitudinal ratings showed that individual
differences in children’s non-pathological dissociation were moderately stable from year to year,
suggesting an individual tendency to dissociate independent of the influence of trauma (BeckerBlease et al., 2004).
50
The role of childhood trauma, and a functional 44-bp insertion/deletion polymorphism in the
promoter region of the serotonin transporter (5-HTT) was investigated among patients with
obsessive-conpulsive disorder (OCD) (Lochner et al., 2007). The 5-HTT gene is one of the main
genes that control serotonergic function, and it has been hypothezised that this gene could play a
role in the development of OCD. Dissociation was measured with the DES (Bernstein and Putnam,
1986), and childhood traumatic experiences were assessed with the Childhood Trauma
Questionnaire (Bernstein et al., 1994). Subscales include emotional abuse, physical abuse, sexual
abuse, emotional neglect and physical neglect. The study analyses indicated that an interaction
between physical neglect and the S/S genotype of the 5-HTT gene significantly predicted
dissociation in patients with OCD (Lochner et al., 2007).
2.5.3. The relationship between psychological and somatoform dissociation
Studies using measurement scales for both psychological dissociation and somatoform
dissociation and various other outcome measures have been carried out in some non-clinical and
clinical samples, but no studies have been published on the general population. The correlation
between both forms of dissociation has been found to be significant (El-Hage et al., 2002; Nijenhuis
et al., 1999; ùar et al., 2000), and researchers have argued for the diagnostic categorization of
conversion disorders (Nijenhuis, 2000; ùar, 2006; Spitzer et al., 1998; Terzan et al., 1998). The
impact of trauma on psychological and somatoform dissociation has been an issue in most of these
studies (El-Hage et al., 2002; Nijenhuis et al., 1998c, 2003; Näring and Nijenhuis, 2005; ùar et al.,
2004; Waller at al., 2000).
Considerable comorbidity with depression among patients with both conversion and dissociative
disorders has been found. The prevalence of reported childhood abuse was also high among these
patients (ùar et al., 2004; Terzan et al., 1998).
2.5.4. Stability of dissociative symptoms
Until now, no studies have been published on the stability of dissociative symptoms at the
population level. In clinical or selected non-clinical samples, DES scores have shown good
temporal stability over shorter periods of time. In small samples of dissociative disorder patients the
correlations have been as high as 0.93 over a period of 2-4 weeks (Frischholz et al., 1990, Van
Ijzendoorn and Schuengel, 1996). Among 26 normal subjects a test/retest reliability of 0.84 was
found over a period of 4-8 weeks (Bernstein and Putnam, 1986). In a study with a sample of 83
51
non-clinical female subjects the interval was one year, and Spearman’s correlation was 0.78
(Putnam et al., 1992).
In a study on a university student sample (n = 465) the stability of the DES scores and the
dissociative taxon membership were assessed with a two-month interval (Watson 2003). The
stability of the DES scores was good (r = 0.69), and the total DES score was 12.5 (SD 9.0) at time 1
and 12.8 (SD 10.5) at time 2. The prevalence of taxon membership (0.90 cut-off criterion) was
1.7% at time 1 and 3.0% at time 2. Altogether, 19 individuals (4.1% of the total sample) could be
classified as taxon members at either time 1 or 2, but only 3 (0.7%) met the criterion at both
assessments. According to these results, the dissociative taxon scores were only modestly stable and
they were substantially less stable than the continuous variables of dissociation (Watson, 2003).
52
3. Aims of the study
Previous general population studies on the prevalence of dissociation have mainly concerned the
psychological aspects of dissociation, and there have been no published data on the prevalence of
somatoform dissociation in the general population. There is controversy over whether psychological
and somatoform dissociation are manifestations of a common construct or different phenomena.
The stability of dissociative symptoms has previously only been investigated in small and/or
clinical samples and with relatively short follow-up periods.
The purpose of this study was to describe dissociation in the general population. The specific
aims of the present study were:
1) To determine the prevalence of pathological dissociation and mean scores of dissociation as well
as factors associated with pathological dissociation among Finnish general population adults.
Sociodemographic factors, depressive symptoms, suicidal ideation and alexithymia were
investigated (Study I).
2) To describe the prevalence of high somatoform dissociation and mean scores of somatoform
dissociation among Finnish general population adults. The impact of sociodemographic factors and
adverse childhood experiences was assessed (Study II).
3) To examine the relationship between psychological and somatoform dissociation in the Finnish
general population (Study III).
4) To describe the course of psychological dissociation during a three-year follow-up among
Finnish general population adults (Study IV).
53
4. Participants and methods
4.1. Study design
This study was part of a population-based longitudinal research project, the Kuopio Depression
(KUDEP) study. The main purpose of the general population arm of the survey was to investigate
the mental health of general population adults, its variations over a three-year follow-up and factors
associated with mental health.
The random general population survey included 3004 adult subjects aged 25-64 years selected
from the National Population Register. The sample was stratified for age, gender and district. All
study subjects were living in the province of Kuopio with a population of 251 000. Study
questionnaires were mailed for the first time in April 1998 accompanied by a letter in which the
study was described in detail. Participation was entirely voluntary. By returning the questionnaire
the respondents gave their informed consent. The data were collected at baseline in May-June 1998
(n = 2050), giving a response rate of 68.2%. Due to incomplete data, 49 subjects were excluded
from the analysis, and the final sample comprised 2001 subjects (Study I). The target measurement
scale for dissociation was the Dissociative Experiences Scale (DES).
In the second phase of the survey in May-June 1999 a second questionnaire was sent to 2945
subjects. Out of the 3004 subjects at baseline, 59 were excluded due to a changed and/or unknown
address (n = 45), refusal to participate (n = 10) or death (n = 4). A total of 1767 questionnaires were
returned, giving a response rate of 60.0%. Due to incomplete data, 28 subjects were excluded from
the analysis. Thus, the sample consisted of 1739 subjects (Study II). The measurement scale for
dissociation was the Somatoform Dissociation Questionnaire (SDQ-20).
The questionnaires for the follow-up were mailed in May-June 2001 to all those who responded
earlier either in 1998 or 1999 (n = 2223). On follow-up, 1618 subjects responded, giving a response
rate of 72.8% (53.9% of the baseline sample of 3004 subjects). After the exclusion of 33 subjects
with incomplete data, the sample comprised 1585 subjects (Study III). The questionnaire sent in
2001 included both the DES and the SDQ-20.
Furthermore, a total of 1534 subjects (51.1% of the baseline sample) responded both at baseline
in 1998 and on follow-up in 2001, but 37 subjects were excluded due to incomplete questionnaires.
The final sample therefore comprised 1497 subjects who responded in both phases (Study IV).
54
Figure 1. Formation of the study population.
Excluded due
to various
reasons n = 59
General population
survey May-June 1998
n = 3004
Responded at baseline
1998 n = 2050
May-June 1999
n = 2945
Responded in 1999
n = 1767
Excluded due
to incomplete
data n = 49
Study I 1998
n = 2001
Excluded due
to incomplete
data n = 37
Responded at
baseline and
follow-up
n = 1534
Responded on
follow-up 2001
n = 1618
Study IV 2001
n = 1497
Study III 2001
n = 1585
Study II 1999
n = 1739
Excluded due
to incomplete
data n = 28
Excluded due
to incomplete
data n = 33
4.2. Study population
4.2.1. Study I
The baseline sample comprised 2001 participants: 885 (44%) men and 1116 (56%) women.
More men (n = 572, 39.3%) than women (n = 382, 25.5%) were nonresponders (p < 0.001). The
nonresponding men were younger than the responding men (42.1 [SD 10.0] yrs vs. 44.8 [10.6] yrs,
p < 0.001), but no respective difference in age was found among women.
55
4.2.2. Study II
The sample included 1739 participants: 742 (43%) men and 997 (57%) women. The mean age of
the respondents was higher than that of the nonrespondents (45.0 [SD 10.5] yrs vs. 41.9 [SD 10.6]
yrs, p < 0.001). More men than women did not participate (48.8% vs. 33.7%, p < 0.001). The
nonresponding men were significantly younger than the responding men (41.9 >SD [email protected] vs. 45.6
>SD [email protected] yrs; p < 0.001), but no such difference was found among women.
4.2.3. Study III
The sample consisted of 1585 subjects: 668 (41%) men and 917 (59%) women. The mean age of
the responders was higher than of the nonresponders (45.0 [SD 10.6] vs. 42.6 [SD 10.6] yrs, p <
0.001).
4.2.4. Study IV
The sample comprised 1497 subjects who responded both at baseline in 1998 and on follow-up
in 2001. There were 624 (42%) men and 873 (58%) women in this sample. On follow-up, more
men than women did not respond (29 vs. 22%, p < 0.001). Both the non-responding men and
women were younger then the respective respondents (in men: mean age 41.9 yrs [SD 10.4] vs.
46.1 yrs [SD 10.4], p < 0.001, and in women: 42.5 yrs, [SD 10.8] vs. 44.5 yrs, [SD 10.8],
p = 0.009). There was no statistically significant difference in the mean DES score at baseline
between the non-responding and responding men (8.5 [SD 9.1] vs. 7.7 [SD 8.0], p = n.s.), but the
mean DES score in the non-responding women was higher than in the responding women (9.7 [SD
10.6] vs. 7.8, [SD 7.6], p = 0.001).
56
Table 5. Sociodemographic characteristics of the subjects in studies I-IV.
Factors
Study I
Study II
Study III
Study IV
N = 2001
N = 1739
N = 1585
N = 1497
Female (%)
56
57
59
58
Age, mean (SD)
44.3 (10.7)
45.0 (10.5)
45.0 (10.6)
45.1 (10.6)
Married or cohabiting (%)
72
73
74
74
Living in an urban area (%)
75
74
75
74
Education • 9 yrs (%)
84
85
84
84
4.3. Methods
All of the methods are described in this section, but not all were used in each individual study.
The exact methods for the separate studies are described in detail in the original publications.
The participants were questioned about their sociodemographic background (sex, age, marital
status and place of residence). In addition, a single question was asked to assess each of the
following factors: years of education (t nine years = high vs. < nine years = low); subjective
working ability (good vs. reduced or unable to work = reduced); financial situation (good or fairly
good = good vs. fairly poor or poor = poor); general health status (good or fairly good vs. fairly
poor or poor), and social support (adequate or fairly adequate vs. inadequate); alcohol consumption
(2-3 times/week or more = frequent vs. once a week or less = seldom); and current smoking (yes vs.
no).
4.3.1. The assessment of dissociation
Dissociative symptoms were assessed with the Dissociative Experiences Scale (DES) and the
Somatoform Dissociation Questionnaire (SDQ-20). The DES was included in study questionnaires
at baseline in 1998 and on follow-up in 2001, and the SDQ-20 was included in questionnaires in
1999 and on follow-up in 2001.
57
4.3.1.1. The Dissociative Experiences Scale (DES)
Dissociative symptoms were evaluated with the Finnish version (Tanskanen, 1997) of the
Dissociative Experiences Scale (DES). The Finnish version was translated first from English to
Finnish, and then back to English. Translation was carried out by an English language teacher at the
University of Kuopio. The scale is a 28-item, self-report instrument for the measurement of
dissociative experiences. The scale takes approximately ten minutes to complete and yields item,
subscale and total scores, which all range from 0 to 100. The individual’s total score is the mean of
the 28 items, and higher scores indicate greater levels of dissociation.
A Dissociative Experiences Scale Taxon (DES-T) with eight items from the DES has been
developed to more clearly distinguish the pathological component of dissociation (Waller and Ross,
1997). A cut-off score of 20 in the DES-T has been suggested to be optimal to distinguish general
population subjects with dissociative disorders (Waller and Ross, 1997; Ross et al., 2002). In Study
I, we selected this cut-off score for pathological dissociation to divide our sample into high
dissociators (DES-T • 20) and low dissociators (DES-T < 20).
In study IV we used both the DES and its subscale DES-T in measuring dissociative symptoms
at baseline and on follow-up. A cut-off score of 20 in the Dissociative Experiences Scale was
selected to indicate high dissociation (Draijer and Boon, 1993; Steinberg et al., 1991). The sample
was categorized into low dissociators with DES scores below 20 and high dissociators with DES
scores of 20 or more. A statistical program was also used to calculate the dissociative taxon
membership probability on the basis of the DES-T scores. Subjects were classified as belonging to
the pathological dissociative taxon if their taxon probability exceeded 90% (Waller and Ross,
1997).
4.3.1.2. The Somatoform Dissociation Questionnaire (SDQ-20)
In study II the level of somatoform dissociation was estimated with a Finnish version of the
Somatoform Dissociation Questionnaire (SDQ-20) (Nijenhuis et al., 1996). The English version of
the SDQ-20 (Nijenhuis et al., 1996) was translated from English to Finnish by Antti Tanskanen
(M.D., Ph.D.), one of the researchers in the study. The SDQ-20 is a 20-item self-report
questionnaire in which an individual is asked to identify to what extent each statement is applicable
to him or her. The score corresponding to the response to each statement ranges from 1 to 5, and the
total score from 20 to 100. From previous research (Nijenhuis et al., 1999; ùar et al., 2000) a cut-off
58
point of 30 in the SDQ was selected to categorize the sample into subjects with high somatoform
dissociation (SDQ •30) and subjects with low somatoform dissociation (SDQ <30).
Both the DES and the SDQ-20 were used in study III. A decile was used to compile equal groups
of subjects with the highest scores in the DES and the SDQ-20 to ensure a sufficiently large sample
size for analysis (Altman and Bland, 1994). In addition, those subjects with high scores in both DES
and SDQ-20 were separated from these two groups. Four groups were thus obtained from the total
sample: LBoth (low dissociation scores in both DES and SDQ-20), HDES (high DES and low
SDQ-20 scores), HSDQ (high SDQ-20 and low DES scores), and HBoth (high DES and high SDQ20 scores).
4.3.2. Depression
Depression has been conceptualized as a syndrome with a range of etiological factors and
comprising disparate symptoms, with disturbances of mood, thinking, sleep, appetite and motor
activity (DSM-IV, APA, 1994; ICD-10, WHO, 1992).
Depressive symptoms were assessed using the 21-item Beck Depression Inventory (BDI) (Beck
et al., 1961, 1988). In this study the sum of total scores was regarded as a continuous variable or
divided into four groups: 0-9 (normal mood), 10-18 (mild depression), 19-29 (moderate depression)
and 30-63 (severe depression). The three groups with scores ranging from 10-63, indicating
subjective symptoms of depression, were combined in multiple logistic regression analysis.
The prevalence of moderate to severe depression measured with the Beck Depression Inventory
was 11.7% in this general population sample (Hintikka et al., 2001a). The reliability of the BDI has
previously been demonstrated to be 0.89 (Cronbach’s alpha) in the same general population sample
(Honkalampi et al., 2000).
On one-year and three-year follow-up, questions were also asked concerning whether a
depressive episode had been diagnosed by a physician during the preceding 12 months, and whether
antidepressant medication had been used during the previous week. Some brand names of drugs
were given as examples.
4.3.3. Suicidal ideation
Suicidal ideation refers to cognitions that can vary from transient thoughts about the
worthlessness of life and death wishes to concrete plans for killing oneself and obsessive
preoccupation with self-destruction (Diekstra and Garnefski, 1995).
59
In this study, suicidal ideation was estimated with item nine of the BDI. The responses “I have
definite plans to commit suicide,” “I would kill myself if I had a chance” and “I feel I would be
better off dead” indicate the presence of suicidal ideation, and subjects choosing these options were
considered suicidal. The response “I have no thoughts of harming myself” indicates the absence of
suicidal ideation.
BDI item 9 has been previously used in screening for suicidal ideation in this general population
sample and has revealed the 12-month prevalence (14.7%) and incidence (4.6%) of suicidal ideation
(Hintikka et al., 2001a).
4.3.4. Alexithymia
The original definition given to alexithymia was the inability to recognize and verbalize
emotions (Sifneos, 1973). A poverty of imagination or of a fantasy world (Haviland and Reise,
1996), as well as a lack of positive emotions and a high prevalence of negative emotions have also
been considered to be characteristic of alexithymia (Taylor, 1994).
In the present study, alexithymia was assessed using the Finnish version (Joukamaa et al., 2001)
of the 20-item Toronto Alexithymia Scale (TAS-20) (Bagby et al., 1994). The total scores of the
TAS-20 were categorized according to the recommendations of Taylor and co-workers (1997); thus,
a score t61 indicated alexithymia, and d51 no alexithymia. Subjects with a TAS-20 score between
51 and 61 were categorized as intermediate. In multivariate analysis the intermediate group was
combined with the nonalexithymic group.
The prevalence of alexithymia in this general population sample has been demonstrated to be
12.8% in men and 8.2% in women (Honkalampi et al., 2000), and 10.0% in men and women
combined (Hintikka et al., 2001b). The reliability (Cronbach’s alpha) of TAS-20 in the same
general population sample was 0.86 (Honkalampi et al., 2000).
4.3.5. Adverse childhood experiences (ACEs)
Six questions were used to assess adverse childhood experiences (Haatainen et al., 2003). The
alternative responses and their classification are presented in parentheses after each question.
60
Poor relationship between parents
The relationship between parents was determined with the question: “What was the relationship
between your parents like in your childhood and adolescence?” (good, fairly good vs. don’t know,
fairly poor, poor and quarrelsome).
Unhappy childhood home
Happiness of childhood home was defined with the question: “Was your childhood home
happy?” (no vs. yes).
Hard parenting
Hard parenting was assessed with the question: “What was the parenting like?” (gentle, fairly
gentle vs. fairly hard, hard).
Physical punishment
Physical punishment (e.g. pulling one’s hair, spanking, birching) was investigated with the
question: “If you were physically punished under 15 years of age, by whom did it happen?” (yes, by
father, by mother, by both parents, by somebody else vs. no, I was not physically punished).
Domestic violence
Domestic violence was assessed with the question: “Have you suffered from domestic violence
directed to you in your childhood or adolescence?” (yes, physical violence, sexual violence, both
physical and sexual violence vs. no, I have not suffered from domestic violence).
Alcohol abuse at home
Alcohol abuse at home was assessed with the question: “Did anybody misuse or abuse alcohol in
your childhood home?” (yes, father, mother, both parents, somebody else vs. no, nobody).
In multiple logistic regression analysis, all the above-mentioned ACEs were studied
independently and by clustering them into three categories (none; one to three; four to six).
4.3.6. Statistical analysis
Data analyses were conducted using the statistical software package SPSS for Windows 11.0 or
11.5 (SPSS, Inc., Chigaco, IL). The results for the continuous variables were given as the mean,
SD, and statistical significance (p-value). A p-value of < 0.05 was considered statistically
significant in the analyses.
Relationships between the continuous variables were assessed with independent-samples t-test,
paired samples t-test, Mantel-Haenszel’s test for linear-by-linear associations, the Mann-Whitney
U-test or by analysis of variance (ANOVA) when appropriate, and Pearson’s (Studies I-III) or
Spearman’s (Study IV) bivariate correlation analysis.
61
The Pearson chi-squared test (with continuity Yates’ correction in Study I) or Fisher’s exact test
were used for categorical variables. Multiple logistic regression analysis (method: enter) was
performed to determine risk factors (OR with 95% CI) for dissociation.
To evaluate the reliability of the measurement scales for dissociation (DES and SDQ-20), a test
of internal consistency (Cronbach’s Į-coefficient) was used in all studies I-IV. Bayesien probability
scores were calculated for the dissociative taxon membership using the SAS program scheme
(Waller and Ross, 1997) that was converted to a SPSS program comm and. All statistical tests
were two-tailed.
62
5. Results
5.1. Pathological dissociation (Study I)
5.1.1. The prevalence of pathological dissociation and mean scores of the DES in the general
population
The prevalence of pathological dissociation (DES-T t20) in the general population was 3.4%,
and there was no statistically significant difference between men (3.6%) and women (3.2%). The
mean total DES score for the entire sample was 8.0 (SD 8.1). The mean total DES score was lower
in men than women (7.8 vs. 8.2, p = 0.034), and it declined slightly but not significantly with age.
5.1.2. Factors associated with pathological dissociation
Depressive symptoms, alexithymia and suicidality had a strong association with pathological
dissociation. Single, divorced or widowed male subjects were quite often high dissociators. A poor
financial situation was associated with pathological dissociation, but the association was
statistically significant only in men. In subjects with a reduced working ability the prevalence of
high dissociators was higher than in those with a good working ability in both genders. Frequent
alcohol consumption was associated with pathological dissociation in women and current smoking
in men.
Multiple logistic regression analysis was performed on four models, each including one
psychiatric symptom variable and the sociodemographic variables, and one model in which all three
psychiatric symptom variables were included. In Model 1, pathological dissociation was
significantly associated with depression. Subjects with depression had a nearly nine-fold greater
risk of pathological dissociation compared with subjects with a normal mood. In Model 2, the
likelihood of pathological dissociation was more than seven-fold greater in alexithymic subjects
compared with subjects without alexithymia. In Model 3, the odds of pathological dissociation were
over four-fold greater among suicidal subjects compared with nonsuicidal subjects. In Model 4, all
three psychiatric symptom variables were included in the same multiple logistic regression model to
assess the significant independent relationships with pathological dissociation. The odds ratios of
pathological dissociation remained statistically significant in depressive (AOR 3.85 [95%CI 1.887.90]), alexithymic (AOR 4.01 [95%CI 2.15-7.49]) and suicidal (AOR 2.19 [95%CI 1.16-4.13])
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subjects. Frequent alcohol consumption had a significant association with pathological dissociation
in all models.
5.2. Somatoform dissociation (Study II)
5.2.1. The prevalence of somatoform dissociation and the mean scores of the SDQ-20 in the
general population
The prevalence of high somatoform dissociation (SDQ-20 t30) was 9.4% in the general
population. The prevalence of somatoform dissociation was higher among men than women (11.1%
vs. 8.2%, p = 0.047). The mean SDQ score was 23.3 (SD 6.1) among the total sample, and it was
higher in men than in women (23.8 [SD 6.9] vs. 22.9 [SD 5.3], p = 0.002). The reliability alpha
coefficient of SDQ-20 was 0.89 in this study.
5.2.2. Sociodemographic variables
The prevalence of high somatoform dissociation increased with age, low education,
unemployment, a reduced working ability and a poor financial situation. In multiple logistic
regression models, the odds for high somatoform dissociation were increased with a reduced
working ability (AOR 3.96 [95% CI 2.59-6.03], p < 0.001) and a poor financial situation (AOR
2.26 [95% CI 1.54-3.32], p < 0.001) among the participants.
5.2.3. Adverse childhood experiences (ACEs)
High somatoform dissociation was more prevalent among women with different adverse
childhood experiences, except for a poor relationship between the parents. Among men, high
somatoform dissociation was associated with a poor relationship between the parents, an unhappy
childhood home and physical punishment.
In multiple logistic regression models, physical punishment (AOR 2.26 [95% CI 1.46-3.48],
p < 0.001) was associated with high somatoform dissociation. There were some differences between
men and women: a poor relationship between the parents (AOR 2.18 [95% CI 1.08-4.42],
p < 0.001) increased the odds of high somatoform dissociation among men, and alcohol abuse in
their childhood home (AOR 1.77 [95% CI 1.03-3.03], p < 0.001) among women.
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The adjusted relative risk (AOR) of high somatoform dissociation was 2.03 (95% CI 0.83-4.95,
p = n.s.) with 1-3 ACEs and 3.05 (95% CI 1.11-3.36, p = 0.030) with 4-6 ACEs among men, while
among women the adjusted relative risk of high somatoform dissociation increased to 2.65 (95% CI
1.16-6.04, p = 0.021) with 1-3 ACEs and 5.43 (95% CI 2.22-13.28, p < 0.001) with 4-6 ACEs.
The prevalence of high somatoform dissociation increased linearly with an increasing number of
ACEs in both genders. It increased from 5.1% to 19.4% among men (p = 0.001), and from 3.4% to
16.6% (p < 0.001) among women with cumulative ACEs.
5.3. The relationship between psychological and somatoform dissociation (Study III)
In study III, subjects with both high somatoform dissociation and psychological dissociation
(HBoth) were compared with subjects with either high psychological dissociation (HDES) or with
high somatoform dissociation (HSDQ). The HBoth subjects had higher mean DES (HBoth: 24.9
>SD [email protected] vs. HDES: 17.3 >SD [email protected], p < 0.001, and HSDQ: 6.3 >SD [email protected], p < 0.001) and SDQ-20
(HBoth: 34.5 >SD [email protected] vs. HSDQ: 28.2 >SD [email protected], p < 0.001, and HDES: 21.9 >SD [email protected], p < 0.001)
scores than subjects in the other groups. They more often reported depressive symptoms, suicidal
thoughts, a reduced working ability, a poor financial situation, poor general health and inadequate
social support compared with subjects in the other groups. The HBoth subjects were also more
frequently single, divorced or widowed compared with the HSDQ subjects. The reliability alpha
coefficients of the DES and the SDQ-20 in this sample were 0.94 and 0.83, respectively. The
Pearson’s correlation between the DES and SDQ-20 scores was 0.60.
Three multiple logistic regression models were used to identify factors that were associated with
HDES, HSDQ and HBoth compared with the LBoth group. Depressive symptoms (AOR 1.99 [95%
CI 1.07-3.72]), suicidality (AOR 2.26 [95% CI 1.14-4.46]) and a younger age (AOR 0.97 [95% CI
0.95-1.00]) were associated with HDES. Factors associated with HSDQ were suicidality (AOR 2.68
[95% CI 1.38-5.21]) and a reduced working ability (AOR 2.20 [95% CI 1.21-4.00]). Depressive
symptoms (AOR 9.19 [95% CI 3.96-21.32]), suicidality (AOR 3.05 [95% CI 1.56-5.96]), a reduced
working ability (AOR 2.59 [95% CI 1.08-6.20]), a younger age (AOR 0.96 [95% CI 0.93-0.99]),
and being single, divorced or widowed (AOR 1.99 [95% CI 1.09-3.63]) were associated with
HBoth.
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5.4. Course of dissociation in the general population (Study IV)
5.4.1. Stability of psychological dissociative symptoms
The majority (98%, n = 1371) of subjects with low dissociation at baseline (n = 1399) were also
low dissociators on follow-up. In 28 subjects (2% of baseline low dissociators) the DES score
increased above the cut-off score (new cases). At the same time, the DES score of 70 subjects (71%
of the 98 baseline high dissociators) decreased below the cut-off score (recovered cases). Twentyeight subjects were constantly high dissociators (stable cases) (29% of the 98 high dissociators at
baseline). Statistically significant differences were detected between the groups for four background
factors: age, working ability, subjective general health and smoking.
With a 0.90 probability cut-off score, 28 (2%, n = 1463) dissociative taxon members could be
identified at baseline and 15 (1%) on follow-up, but only four (0.3%) subjects met the criteria in
both assessments.
There was no statistically significant change in the mean DES (35.9 [SD 13.2] vs. 32.0 [SD
10.0], p = n.s.) or DES-T (27.4 [SD 16.4] vs. 24.0 [SD 11.3], p = n.s.) score between baseline and
follow-up in stable cases. However, the changes in DES and the DES-T scores were significant
among new (DES: 9.0 [SD 4.8] vs. 29.7 [SD 11.0], p < 0.001; DES-T: 4.4 [SD 3.3.] vs. 22.9 [SD
14.3], p < 0.001) and recovered (DES: 28.4 [SD 7.8] vs. 9.9 [SD 5.5], p < 0.001; DES-T: 19.0 [SD
11.1] vs. 4.6 [SD 4.4], p < 0.001) cases.
5.4.2. Associations between dissociation, depressive symptoms and suicidal ideation
There was no significant change among recovered cases in the mean BDI score (12.4 [SD 9.8]
vs. 10.2 [SD 8.4], p = n.s.) or the prevalence of suicidal ideation (22.9% vs. 20.0%, p = n.s.) during
the follow-up period. However, in new cases the mean BDI score (9.2 [SD 9.6] vs. 16.7 [SD 14.3],
p = 0.011) and the prevalence of suicidal ideation (21.4% vs. 35.7%, p = 0.013) increased
significantly during the follow-up. In stable cases, no significant difference was recorded between
any of the variables, the mean BDI score was at a high level (15.8 [SD 10.2] vs. 18.3 [SD 11.7],
p = n.s.), and half of the cases had suicidal thoughts (53.8% vs. 46.4%, p = n.s.). In low
dissociators, significant declines were observed in the mean DES score (6.1 [SD 4.3] vs. 4.4 [SD
3.7], p < 0.001) and the prevalence of suicidal ideation (9.0% vs. 6.9%, p < 0.001), but there was no
change in the mean BDI scores during the follow-up (4.8 [SD 5.7] vs. 4.9 [SD 6.2], p = n.s.).
66
In the group of stable cases there was an increase in the proportion taking antidepressant
medication (15.4% vs. 26.9%, p = 0.047), but no change in the diagnosis of depression (34.6% vs.
38.5%, p = n.s.) between baseline and follow-up. Among recovered cases the prevalence of a
diagnosis of depression (13.1% vs. 9.8%, p = 0.002) and the use of antidepressant medication
(14.8% vs. 11.5%, p < 0.001) significantly declined, but among the new cases the diagnosis of
depression (16.7% vs. 37.5%, p = 0.012) was made more frequently, and they more often used
medication for depression (20.8% vs. 29.2%, p = 0.014) after the follow-up period.
Stable high dissociation was associated with an increase in the BDI score (AOR 1.08 [95% CI
1.02-1.14], p = 0.008) and with suicidal ideation (AOR 6.39 [95% CI 2.49-12.39], p < 0.001), a
younger age (AOR 0.93 [95% CI 0.88-0.98], p = 0.004), a reduced working ability (AOR 4.76
[95% CI 1.56-14.48], p = 0.006) and smoking (AOR 2.83 [95% CI 1.17-6.86], p = 0.021) at
baseline. Becoming a new case was predicted by an increase in the BDI score (AOR 1.13 [95% CI
1.08-1.18], p < 0.001), and by a younger age (AOR 0.94 [95% CI 0.89-0.98], p = 0.011), and a
reduced working ability (AOR 4.66 [95% CI 1.62-13.39], p = 0.004) at baseline. No factor was
found to explain the recovery from dissociation in this model. However, when we compared stable
with recovered cases, recovery from high dissociation was predicted by a decline in the BDI score
during the follow-up (AOR 0.92 [95% CI 0.87-0.98], p = 0.01) and by having no suicidal thoughts
(AOR 0.19 [95% CI 0.51-0.70], p = 0.012), an older age (AOR 1.10 [95% CI 1.02-1.18], p = 0.01),
and a good working ability (AOR 0.18 [95% CI 0.03-0.94], p = 0.041) at baseline.
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6. Discussion
6.1. Prevalence of dissociation in the general population
The prevalence of pathological dissociation in Finland (3.4%) was at the same level as in studies
on the North American general population with the same cut-off score of 20 in the DES-T (Seedat
et al., 2003). The mean DES-T score in our study (3.8 [SD 6.9]) was also similar to that reported by
Seedat and coworkers (3.5 [SD 8.6]), but higher than the mean DES-T score in a recent non-clinical
study in Germany (2.3 [SD 4.2]) (Spitzer et al., 2006). There have been no previous published
studies on the prevalence of pathological dissociation in European general population samples.
Total dissociation (DES and DIS-Q) scores or the estimated prevalence of psychological
dissociation have tended to be lower in Europe than in North America (Akyüz et al., 1999; Ross et
al., 1990; Spitzer et al., 2006; Vanderlinden et al., 1991, 1993). However, in a Turkish general
population of female participants the prevalence of high dissociation was as high as 15.9% (total
DES score >20), and the mean DES score was 11.8 (SD 10.2 (Akyüz et al., 2005). By contrast, the
total DES score was as low as 2.6 (SD 4.3) in a Chinese non-clinical population of factory workers
(Xiao et al., 2006a, b).
The prevalence of dissociative taxon membership in our follow-up study was lower (2% at
baseline and 1% on follow-up) than in North America (Waller et al., 1997), but considerably higher
than in Germany (Spitzer et al., 2006) or China (Xiao et al., 2006a, b). The non-clinical samples
were smaller (Spitzer et al., 2006; Xiao et al., 2006a, b) than our general population sample, and the
generalization of the results of selected samples has more limitations than with a general population
sample. According to the predictions of the trauma model of dissociation, (1) pathological
dissociation occurs in all cultures, and (2) within any given culture, it is more frequent in samples
with higher levels of childhood trauma (Xiao et al., 2006 a). The sociocognitive model, on the other
hand, predicts that pathological dissociation is unrelated to childhood trauma and arises from one of
two sources: (1) expectations and demand characteristics imposed by mental health professionals,
and (2) significant popular knowledge of pathological dissociation, especially dissociative identity
disorder, which influences susceptible individuals to role enact the expected symptoms and
behaviours (Xiao et al., 2006a, Spanos, 1994). In central-eastern Finland, almost no public
knowledge exists concerning dissociative disorders, the possibility of role demands or iatrogenic
suggestion. However, the prevalence of pathological dissociation was at the same level as in North
America, where dissociative symptoms and especially the dissociative identity disorder (DID) have
gained more widespread public knowledge. The high prevalence of dissociative experiences among
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women from rural districts of Turkey (Aküyz et al., 2005) with a concomitant high prevalence of
childhood abuse in that sample does not support the sociocognitive model of dissociation, either.
The socio-cognitive model has gained little empirical support (Dell, 2006b; Gleaves, 1996).
To my best knowledge, no previous studies have examined the prevalence of somatoform
dissociation in a general or non-clinical population. The prevalence of high somatoform
dissociation in our study was quite high (9.4%), suggesting that somatoform dissociative symptoms
are common at the population level. The mean SDQ-20 score in our study (23.3 [SD 6.1]) was at
the same level as in a random Dutch non-clinical sample (23.2 [SD 5.0]; Näring and Nijenhuis,
2005), but lower than in a Turkish non-clinical sample (ùar et al., 2000), in which the mean SDQ20 score was 27.4 (SD 8.2).
6.2. Factors associated with dissociation
6.2.1. Age
Pathological dissociation was not associated with age in our Study I. In addition, there was no
statistically significant association between age and the total DES score. These results differ from
previous studies, where DES (Ross et al., 1990) or DES-T (Seedat et al., 2003) scores have declined
with age. The age range in our study did not include subjects from eighteen to twenty-five years of
age, and this might influence the associations with age, as younger subjects have scored
significantly higher in the DES (Ross et al., 1990).
The prevalence of high somatoform dissociation increased with age in our Study II, which is
contrary to previous studies in which age did not affect the SDQ-20 scores (Nijenhuis et al., 1996,
1998a). In a Turkish patient study (ùar et al., 2000) a weak positive correlation between high
somatoform dissociation and older age was found. However, the previous studies have been
performed on small, heterogeneous samples, and no studies at a population level have been
published. There is a possibility that older, less educated subjects could report more frequent
somatic symptoms, and this might also have influenced our SDQ-20 scores, although it has been
shown that somatoform dissociation cannot be equated with a tendency to report physical
complaints (Nijenhuis et al., 1999). In the Dutch study, however, due to the male/female ratio and
the mean ages in the diagnostic groups, older male subjects were poorly represented.
In Study III, subjects with high somatoform dissociation were significantly older than subjects
with high psychological dissociation. However, a younger age predicted simultaneous high
somatoform and high psychological dissociation (HBoth), and these subjects also had the highest
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scores in both DES and SDQ-20, indicating the highest levels of dissociative symptoms. In the
follow-up study (Study IV), a younger age also predicted stable high dissociation and the risk of
becoming a new case in the follow-up period.
6.2.2. Sex
The total DES score was higher in women than men, but gender did not affect the DES-T scores
in Study I. Our results with the DES subscales were similar to a study with a large, selected German
sample (Spitzer et al., 2003): men scored higher in the amnesia subscale compared with women,
and there was no gender difference in the DES-T scores. The gender difference in the amnesia
subscale was also found in a Dutch population sample (Vanderlinden et al., 1991). As dissociative
amnesia represents a diagnostic criterion for posttraumatic stress disorder (PTSD), it may be that
men and women react differently to traumatizing events, and there may be gender differences in the
storage, consolidation and retrieval of traumatic memories (Spitzer et al., 2003). The total DES
score, the scores for the absorption and imaginative involvement factor, and the nonpathological
part of the DES were higher in women than men in our study. Our results suggest that the
pathological aspects of dissociative experiences are equally common in both genders, but the
nonpathological dissociative symptoms are more prevalent among women.
Men scored significantly higher than women in the Somatoform Dissociation Questionnaire,
which is contrary to previous studies in Dutch samples, where gender did not affect the SDQ-20
scores (Nijenhuis et al., 1996, 1998a). Young men were the least likely to respond to our
questionnaires, and this might also have influenced the results obtained for the DES, DES-T, and
SDQ-20 scores, but in different directions due to the different associations with age.
6.2.3. Socioeconomic and marital status
Apart from the negative association with age, sociodemographic factors have not generally been
associated with high psychological dissociation (Ross et al., 1990). Pathological dissociation had
significant bivariate associations with several factors in Study I, but in logistic regression analysis
only subjective work disability had a significant relationship with pathological dissociation.
High somatoform dissociation was associated with a low educational level, reduced working
ability or poor socio-economic status, and a similar trend compared with our results was found in a
Turkish patient study (ùar et al., 2000). In Study III, subjects with both high psychological and high
somatoform dissociation (HBoth) had considerable adversities in their health, working ability and
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financial and social situation compared to other groups. The HBoth subjects probably had a cluster
of dissociative symptoms typical of either complex post-traumatic stress disorder or dissociative
disorders (ùar et al., 2004; Van der Hart et al., 2006), which significantly affected their lives.
Reduced working ability also strongly predicted stable high dissociation in the follow-up study,
which further supports the impact of dissociative pathology on the individual’s daily functional
capacity.
6.2.4. Substance use (alcohol and tobacco)
Although frequent alcohol consumption had a significant relationship with pathological
dissociation in the cross-sectional study (Study I), it was not associated with stable high dissociation
in the follow-up study (Study IV). However, smoking was common among stable high dissociators,
and there was an almost three times greater risk for being a stable high dissociator among baseline
smokers compared to nonsmokers. Although rates of smoking among populations with psychiatric
disorders are more than twice as high as among the general population, the mechanism of this
relationship is not yet clear, and there have been virtually no published studies on the association
between smoking and dissociation. In a study with male prison inmates, self-cutting inmates had
begun smoking and other substance abuse earlier than non-cutters and also scored higher in the
Adolescent Dissociation Experiences Scale (A-DES) (Matsumoto et al., 2005). Post-trauma mental
health disturbances such as post-traumatic stress disorder (PTSD) have been associated with
increased smoking (Breslau et al., 2003), either by starting to smoke or an increase of tobacco use.
In addition, the effect of smoking on PTSD symptoms has been examined (Buckley et al., 2007),
and smoking has been found to be an independent risk factor for severe anxiety and hostility
symptoms and subsequent PTSD among adult disaster victims and for anxiety symptoms among
adult people who are confronted with stressful life events (Van der Velden et al., 2007). Smoking
may also be a coping mechanism to reduce distress caused by traumatic or stressful events.
However, in our study IV, no trauma variables were included, so no definite conclusions about the
interesting association between smoking and stable high dissociation can yet be drawn.
6.3. Comorbidity between dissociation, depressive symptoms and suicidal ideation
In Studies I, III and IV a strong relationship between high levels of dissociation, depressive
symptoms and suicidal ideation was observed, supporting earlier findings that dissociative
pathology is linked with substantial comorbidity (Mulder et al., 1998; Nijenhuis et al., 2003; ùar et
71
al., 2004; Saxe et al., 1993). In cross-sectional Study I the risk of pathological dissociation was
increased almost nine-fold with current depressive symptoms and four-fold with suicidal ideation.
The association between dissociation and depressive symptoms in HBoth subjects was striking:
80% of them had BDI scores suggestive of current depression and half of them had suicidal
thoughts (Study III). The relationship between dissociation, depressive symptoms and suicidal
ideation was as significant in the follow-up study (Study IV) as in the cross-sectional studies
(Studies I and III). Stable cases had long-lasting high mean BDI scores, half of them had persistent
suicidal ideation, and the frequency of antidepressant medication use among them was high and
even increased during the follow-up period. The dissociative symptoms probably remained
unrecognized, because dissociative disorders have rarely been diagnosed properly (Foote et al.,
2006; Lipsanen et al., 2004a). For example, in 2000 there were 99 inpatients in Finland who had
been diagnosed as having a dissociative disorder (3‰ of all inpatients, total n = 32669) (National
Research and Development Centre for Welfare and Health, 2001), while the estimated prevalence
of dissociative disorders in inpatients has ranged from 4-21% (Foote et al., 2006; Ross et al., 1991).
6.3.1. Comorbidity between dissociative experiences and depressive symptoms
Pathological dissociators have been found among patients with affective, anxiety and
somatoform as well as personality disorders, and they have had more psychopathological
impairment than non-pathological dissociators (Spitzer et al., 2006). An explanation for the
comorbidity of dissociation might be adaptation to stress and the consequences of experiencing
traumatic events (Anderson et al., 1993; Ellason et al., 1996; Francia-Martinez et al., 2003; Van der
Kolk et al., 1996; Yargic et al., 1998). In the general population the relationships between high
dissociation, psychiatric comorbidity and childhood abuse have been examined with somewhat
controversial results (Akyüz et al., 1999; Mulder et al., 1998; ùar et al., 2007).
In the Turkish general population, no statistically significant association between high
dissociation (DES >17) and major depression (or any other diagnosis except dissociative disorders)
was found, and only childhood neglect and all types of childhood abuse combined were associated
with high dissociation (Akyüz et al., 1999). The major limitation in that study was a significant loss
of participants in the interviewing process, and small eventual study groups (Akyüz et al., 1999). A
more recent epidemiological study in the same region of Turkey comprised only female subjects
(ùar et al., 2007), and lifetime major depressive disorder was the most prevalent comorbid diagnosis
among the participants with dissociative disorders. Other diagnostic groups associated with a
diagnosis of dissociative disorders were somatization disorders, borderline personality disorder and
72
PTSD. Of the abuse variables, sexual abuse, physical neglect and emotional abuse were associated
with a diagnosis of a dissociative disorder (ùar et al., 2007).
High dissociation (modified version of the DES and interviews) was associated with both
childhood abuse and current psychiatric illness (mood, anxiety, substance use disorders and PTSD)
in the general population of New Zealand (Mulder et al., 1998). However, in logistic regression
analysis only physical abuse and current psychiatric DSM-III-R disorder were associated with high
dissociation. Sexual abuse was indirectly associated with high dissociation: it was related to both
physical abuse and the current mental state. A direct causal relationship between childhood sexual
abuse and dissociation was argued, but the comorbidity of high dissociation was evident (Mulder et
al., 1998). A recent study on a non-clinical sample of young adults also showed that combined
exposure to parental verbal aggression and witnessing domestic violence was associated with an
extraordinarily large effects size on dissociation, and the association was even stronger than with
familiar sexual abuse. The effect sizes were almost as strong on depression (Teicher et al., 2006).
The differing results reported above may reflect cultural differences, differences in study design
and procedure, or the definitions of high dissociation and childhood abuse. These studies also
illustrate the difficulties in using retrospective reports of childhood traumatisation (Akyüz et al.,
1999; Mulder et al., 1998; Vanderlinden et al., 1993), but it seems that there is reliable evidence of
associations between dissociation, depression and childhood traumatization. Our studies did not
include diagnostic procedures or trauma variables, but they demonstrated significant associations
between high dissociation, depressive symptoms and suicidality cross-sectionally and on follow-up.
Patients with dissociative disorders have many concurrent comorbid diagnoses, because the
diagnostic criteria for these categories do not exclude each other. On the other hand, the excessive
descriptive comorbidity might be reflecting different facets of a single multifaceted psychiatric
condition, the clinical expression of adult psychopathology related to childhood trauma (Herman,
1992). Patients with dissociatiative disorders report the highest frequency of childhood trauma
among all psychiatric categories (Ross et al., 1989), and have extensive psychiatric comorbidity in
both DSM axels (Ellason et al., 1996). Particularly trauma that occurs early in the life cycle can lead
to complex characterological adaptations, as well as disturbed regulation of affective arousal (poor
impulse control, self-mutilating behaviour), an impaired capacity for cognitive integration of
experience (as in dissociation), and impairment in the capacity to differentiate relevant from
irrelevant information, which occurs in the misinterpretation of somatic sensations (Van der Kolk et
al., 1996).
Because dissociation has been difficult to define and disentangle from other psychological
constructs, one perspective opposing the trauma theory has suggested that dissociative phenomena
73
are non-specific and can be found in a variety of other disorders (Fahy 1988; Fahy et al., 1989). One
study has addressed this issue with multiple measures of dissociative experiences and a variety of
theoretically-related constructs (antisocial, borderline, PTSD, depression, and anxiety) in a sample
of 225 college students. Similar difficulties with discriminant validity were found in all
measurement scales, not just with the measurement scales of dissociation. The data supported the
construct-related validity of three dissociation instruments, and offered moderate evidence that
although dissociation was highly associated with other constructs, it could be seen as a distinct,
valid and reliable phenomenon in a non-clinical sample (Gleaves et al., 2000).
6.3.2 The relationship between psychological and somatoform dissociation
The relationship between psychological and somatoform dissociation has not been studied in the
general population, but comorbidity among patients with concomitant conversion and dissociative
disorders have been examined in two studies (ùar et al., 2004; Terzan et al., 1998). ùar and
coworkers (2004) included both the SDQ-20 and DIS-Q in their study design, while the other study
(Terzan et al., 1998) included the DES, as well as diagnostic interviews for dissociative disorders
and comorbid symptomatology. In both studies a simultaneous diagnosis of a conversion disorder
and dissociative disorder meant more severe psychopathology compared to patients with mere
conversion disorder: high comorbidity with depression (ùar et al., 2004; Terzan et al., 1998) and
more suicide attempts and self-mutilative behaviour (ùar et al., 2004). Our results in Study III are in
agreement with these studies, indicating greater psychopathological impairment among HBoth
subjects compared to other groups.
6.3.3. The relationship between dissociation and suicidal ideation
Childhood trauma and neglect were found to be associated with suicide attempts and selfmutilation in a sample of the female general population in Turkey (Aküyz et al., 2005). In that
study, physical neglect and sexual abuse of different childhood trauma types were associated with
higher DES scores among the participants. Furthermore, dissociation had a mediating role between
childhood sexual abuse and a variety of mental health outcomes, including suicidality, sexual
aggression and self-mutilation among adolescents (Kisiel and Lyons, 2001).
Dissociation is a frequent concomitant of self-injury. Many patients report feeling numb and
“dead” prior to harming themselves (Pattison and Kahan, 1983). They often claim not to experience
pain during self-injury and report a sense of relief afterwards (Favazza and Conterio, 1988; Pattison
74
and Kahan, 1983). Episodes of self-mutilation often follow feelings of disappointment or
abandonment (Favazza and Conterio, 1989). In contrast to self-injury, suicide attempts are reported
not to provide relief, to be repeated less frequently, and to have less communicative value (Pattison
and Kahan, 1983). Persistent suicidal ideation has been demonstrated to be associated with a
markedly increased probability of planned suicide attempts at the population level (Kessler et al.,
1999). In a 12-month follow-up study on the Finnish general population, suicidal ideation was
observed to be common and persistent (Hintikka et al., 2001b).
Apart from the high prevalence of persistent suicidal ideation in stable high dissociators in our
Study IV, the frequency of suicidal ideation remained at 20% in the recovered cases despite the
significant decline in the dissociation scores during the three-year follow-up period. These results
suggest that suicidal ideation was a more enduring feature in some subjects in our follow-up study,
who might at the same time experience more state-like dissociative symptoms. The recovered cases
received a diagnosis of depression and used antidepressants less frequently at the three-year followup point. The decline in the DES scores could be a result of a positive treatment outcome in some
individual subjects, because psychiatric treatment has been shown to reduce depressive symptoms
in dissociative identity disorder patients (DID) (Coons and Bowman, 2001; Ellason and Ross,
1997). Suicide ideation was not assessed in these studies. There was a significant reduction in
diagnosed depression in recovered cases over the follow-up, but we consider it unlikely that this
could be the cause of the recovery from dissociation in all 70 cases. The factors associated with
recovery from dissociation require further research.
6.4. The relationship between dissociation and alexithymia
Contradictory views concerning the associations between alexithymia and dissociation have been
reported in different clinical (Grabe et al., 2000, Tutkun et al., 2004; Wise et al., 2000) and nonclinical (Elzinga et al., 2002; Irwin and Melbin-Helberg, 1997; Modestin et al., 2002) samples, but
to my knowledge no reports have been published on general population samples. In our Study I,
alexithymia had a statistically significant association with pathological dissociation in both genders,
and the risk for pathological dissociation was greater in alexithymic subjects compared with nonalexithymic subjects even after adjusting for depression and several other covariates in logistic
regression analysis. However, we did not differentiate between the three factors of alexithymia or
investigate their associations with pathological dissociation. Our results therefore provide no further
evidence concerning whether the factor ‘difficulty identifying or describing feelings’ was associated
75
with pathological dissociation, as has previously been postulated (Elzinga et al., 2002; Irwin and
Melbin-Helberg, 1997; Modestin et al., 2002).
Grabe and coworkers (2000) found that alexithymia predicted pathological dissociation, but their
article did not explicitly mention how dissociation was categorized into ‘pathological’ and ‘nonpathological’ forms or how they calculated their total dissociation scores. However, they suggested
that pre-existing alexithymic features might modulate the individual stress response to distressing or
traumatic experiences in a dysfunctional way, thus increasing the risk for pathological dissociation.
In a study including the DES (DES-T) and the SDQ-20, no associations between pathological
dissociation and alexithymia were found after controlling for age, gender and general
psychopathology, but somatoform dissociation remained significantly related to alexithymia
(Clayton, 2004).
According to Nemiah (2000), in the alexithymic individual, stress-induced arousal undergoes no
psychic elaboration and is directly transformed into a somatic dysfunction, but psychic conversion
symbolically represents the original stressful situation. Despite the differences, both models of
symptom formation are psychological in nature. Both use a psychological model that perceives
symptoms as the end result of stress-induced internal psychic arousal in the form of peripheral
somatic manifestations. Alexithymia and dissociation may both be viewed as a defence against
over-whelming experiences. In this context, alexithymia is termed secondary alexithymia to
differentiate the construct from primary alexithymia, which has been assumed to be genetic or
biological in origin (Freyberger, 1977).
Other explanations for the association between dissociation and alexithymia have been proposed.
Irwin (1997) stated that people with dissociative tendencies have a ‘normal’ affective vocabulary
but have difficulty utilizing this vocabulary to depict their own affective states. This suggests that
the verbal processing system tends to be dissociated from affective processes, additionally
indicating that alexithymia involves the inability to link personal states to emotional words
(‘difficulty identifying and describing feelings’). The isolation of painful affects in dissociation and
secondary alexithymia states, possibly potentiated with depressed mood, may be the common
element. However, the contradictory results from studies that found no association between
dissociation and alexithymia (Tutkun et al., 2004), and associations weakened by confounding
general psychopathology (Wise et al., 2000), have indicated that dissociation fundamentally differs
from alexithymia in that dissociation involves a change of one’s self, whereas alexithymia reflects a
cognitive state of externally-oriented thinking with an inability to identify and report discrete
emotions (Wise et al., 2000). The relationship between dissociation and alexithymia merits further
76
study, taking into account possible gender differences, the factor structure of alexithymia and
possible associations with somatoform dissociation (Clayton, 2004).
6.5. The impact of adverse childhood experiences (ACEs) on somatoform dissociation
In addition to the associations between single adverse childhood experiences (ACEs) and
somatoform dissociation, we measured the impact of multiple ACEs and found a strong, graded
relationship between high somatoform dissociation and an increasing number of ACEs in both
genders. In a previous study the conversion disorder patients who reported multiple types of
childhood traumatization scored significantly higher in the SDQ-20 than conversion disorder
patients with a single type of traumatization (Roelofs et al., 2002). As a large ACE study (Dube et
al., 2001; Felitti et al., 1998) has shown, simultaneously considering the impact of multiple
experiences is important, because ACEs are strongly interrelated and also related to poor physical
and mental health. A review article in which adult retrospective reports of more than one form of
child maltreatment were assessed also showed that the maltreatment types do not occur
independently, and that a significant proportion of individuals experience not just repeated episodes
of one type of maltreatment, but are likely to be victims of other forms of abuse and neglect
(Higgins and McCabe, 2001). The impact of parental verbal aggression on dissociation and limbic
irritability was assessed in a recent study on a non-clinical population of late adolescents (Teicher et
al., 2006). While verbal aggression was associated with moderate to large effects, multiple forms of
abuse were associated with very large effect sizes, with an effect size that was often greater than the
component sum (Teicher et al., 2006).
We found a strong association between somatoform dissociation and physical punishment among
both men and women. Domestic violence, including both sexual and physical violence in
childhood, had a bivariate association with high somatoform dissociation, but the association was
not significant in multiple logistic regression in our population-based sample. It has been suggested
that somatoform dissociation would be more clearly associated with physical abuse where there is a
threat of inescapable physical injury, and somatoform dissociation could be understood as a set of
adaptive psychophysiological responses to trauma (Waller et al., 2000). The frequency of sexual
abuse reported by both genders in our study was low, which gives reason to assume that the results
reflect under-reporting. The other limitation in this issue may be the possibility of recall bias. It
would have been more justifiable to use validated questionnaires (Bernstein et al., 1994; Nijenhuis
et al., 1998c) concerning ACEs to obtain more reliable results for comparison with previous studies.
77
Therefore, the significance of the results obtained from the ACE items in our study should be
considered as limited.
Biological studies have demonstrated the long-lasting consequences of childhood maltreatment
and neglect on the developing brain. They have shown that postnatal neglect or maltreatment
provokes a cascade of stress responses that organize the brain to develop along a specific pathway
selected to facilitate reproductive success and survival in a world of deprivation and strife. This
pathway, however, is costly because it is associated with an increased risk of developing serious
medical and psychiatric disorders and is unnecessary and maladaptive in a more benign
environment (Teicher et al., 2002).
6.6. The stability of dissociative symptoms
Dissociative symptoms were quite stable in our three-year follow-up study. The correlation
(r = 0.62) was on the same level as in a study with a student sample (n = 465) over two months
(r = 0.65) (Watson, 2003). The changes in DES-T scores followed a similar pattern to those of total
DES scores in all our study groups (Study IV). Dimensionally, the DES-T and the overall DES
scores therefore behaved similarly. The DES was originally developed to examine dissociation as a
continuum and was explicitly constructed to be a stable trait measure (Carlson and Putnam, 1993).
The stability of DES scores has been very good over shorter periods of time (Frischholz et al., 1990,
Van Ijzendoorn and Schuengel, 1996), but has not previously been studied over such a long followup period or in the general population. In Study IV, characteristically different groups could be
detected. Stable high dissociators (2% of the whole sample and 29% of baseline high dissociators)
had the highest DES scores and considerable comorbidity, which is already discussed elsewhere.
The relationship between DES scores, BDI scores and suicidal ideation along with the
corresponding changes in the prevalence of diagnosed depression and suicidal ideation further
corroborates the comorbidity of dissociative symptomatology. However, it is not possible to
determine causality, for example whether depression actually gave rise to increased dissociation, or
whether the worsening dissociative symptoms made the subjects more depressive. The changes in
DES scores over the follow-up period were distinct in the new and recovered cases; the participants
either had significantly elevated DES scores or low scores, a result already previously reported
(Waller and Ross, 1997).
The vast majority of our study subjects had constantly very low dissociation scores, and a small
proportion of individuals suffered from persistent dissociative symptoms. The pathological
dissociative symptoms showed similar changes to those in the total DES scores, but the stability of
78
the other factors of the DES should also be studied further. A proportion of individuals had
significantly changing scores over the follow-up period, indicating that these individuals had a
tendency to experience more transient, state-like dissociative symptoms.
6.7. A categorical or dimensional construct?
The stability of the dissociative taxon membership was low. Only four subjects met the criteria
for taxon membership suggested by Waller and Ross (1997) at baseline and on follow-up, and most
of the individuals who were classified as taxon members in one assessment were identified as
nonmembers in the other. Thus, dissociative taxon membership showed less stability than the
continuous variables of dissociation.
Waller and coworkers (1996) stated that there are fundamentally two categorically different
types of dissociation and two types of dissociators. On the basis of their taxometric analyses they
determined that markers of non-pathological dissociation such as absorption and imaginative
involvement measure a dimensional construct, whereas markers of pathological dissociation such as
indicators of amnesia for dissociative states, derealization, depersonalization, and identity alteration
measure a latent class or typological construct. This supports the original view of Janet that there
are two types of individuals: those who experience chronic dissociative states and those who do not.
The former would be members of a pathological dissociative taxon (Waller et al., 1996).
One of the currently most controversial issues in the study of dissociative phenomena is whether
dissociation is a dimensional or a categorical construct. However, recent studies testing the taxonic
model have found little support for the theory of dissociation as a categorical construct. Watson
(2003) concluded that the dissociative taxon scores were only modestly stable and were
substantially less stable than the continuous variables of dissociation among college students during
a two-month period. Our results were similar, although the follow-up time was considerably longer
in our study. Furthermore, in a sample of 276 students and 204 psychiatric inpatients, the ability of
taxon membership to detect dissociative disorders (DD) was investigated on the assumption that
patients suffering from DD should be taxon members (Modestin and Erni, 2004). No statistically
significant relationship was found between taxon membership and the clinical diagnosis of a
dissociative disorder. Taxon membership indicated a higher frequency of dissociative experiences
but could not be equated with the presence of a dissociative disorder (Modestin and Erni, 2004).
Taxon membership probabilities were also only modestly associated with a depersonalization
disorder diagnosis (Simeon et al., 2003). However, different results have also been obtained. Taxon
membership showed good discriminant validity with respect to dissociative disorder diagnosis and
79
reported childhood abuse among 100 traumatized female outpatients, and elevated absorption scores
were also found in subjects with emotional abuse (Allen et al., 2002).
The categorical approach has added to our understanding of dissociative phenomena and future
research will reveal the justification of this theory. Our results question its validity, and perhaps a
hybrid of the two conceptualizations may prove to be more accurate, while much of current research
is based on the premise that dissociation is a continuous variable across both clinical and nonclinical groups.
6.8. Methodological considerations
6.8.1. Study population and design
The population sample was a random sample of the inhabitants of the province of Kuopio in the
central-eastern part of Finland. The age of the study subjects at baseline was limited to between 25
to 64 years, thus covering the entire period of adulthood except for the elderly. The sample size was
larger than in any previous general population studies on dissociation, and the age range was also
slightly different from other studies (Akyüz et al., 1999; Ross et al., 1990; Seedat et al., 2002).
The response rates in our study were satisfactory. In the cross-sectional studies the response rates
were 68% (Study I), 60% (Study II), and 73% (Study III). In the follow-up, 51% of the initial
sample and 75% of the baseline respondents returned the questionnaire (Study IV). In Studies I-III,
more women than men responded to the questionnaire, and among males the respondents were
slightly older than the non-respondents. In Study IV both the non-responding men and women were
younger than the respondents. There was no statistically significant difference in the mean DES
score at baseline between the non-responding and responding men on follow-up, but the mean DES
score of the non-responding women was statistically higher than that of the responding women. The
loss of younger men at baseline and on follow-up is a limitation in generalizing our results to the
general population because of the negative association between the DES scores and age (Akyüz et
al., 1999; Ross et al., 1990). The difference in the DES scores between the responding and nonresponding women on follow-up also possibly indicated that some women with a high DES score
dropped out of the study.
80
6.8.2. The Dissociative Experiences Scale and Somatoform Dissociation Questionnaire
In this study both the DES and the SDQ-20 were found to have satisfactory internal consistency
in all phases. Psychometric evaluation of the DES has been performed in several previous studies
(Carlson and Putnam, 1993; Dubester and Braun, 1995; Van Ijzendoorn and Schuengel, 1996). Its
reliability has been very good, with a mean alpha reliability from 16 studies of 0.93 (Van
Ijzendoorn and Schuengel, 1996). The reliability coefficients in our studies were at the same level,
and the correlation was satisfactory between the DES scores in both phases (r = 0.62), both
indicating good homogeneity of the DES in our study. The psychometric evaluation of the Finnish
version of the DES has also been examined (Lipsanen et al., 2003). The Finnish version of the DES
in our study was translated into English and back into Finnish, and has been published on the web
site of the Sidran Institute (Tanskanen, 1997).
The internal consistency and convergent validity of the SDQ-20 (Nijenhuis et al., 1996, 1999),
and its construct validity has been measured (Nijenhuis et al., 1998b). The reliability alpha
coefficients in our Studies II and III were at a slightly lower level than in some previous studies
(Nijenhuis et al., 1996, 1998b; ùar et al., 2000), and in a recent study (Espirito Santo and PioAbreu, 2007), although similar results to ours have also been reported (El-Hage et al., 2002; Waller
et al., 2000).
ùar and coworkers (2000) detected a test-retest Pearson’s correlation over one month of r = 0.95,
but their study included only 35 subjects. Spearman’s correlation between the SDQ-20 scores in our
two studies was lower (r = 0.51). These results indicate satisfactory reliability of the SDQ-20. The
Finnish version of the SDQ-20 was translated from English into Finnish by Antti Tanskanen (M.D.,
Ph.D.), but no translation back into English was performed. The current English version of the
SDQ-20 is published in a book by Ellert Nijenhuis (2004) and in one of his articles (2000). It has
also included questions on whether the phenomena in the statements are related to a known physical
illness. However, that version of the SDQ-20 is used more in the clinical work with patients than in
research. The order in which the statements are presented has no impact on the results (Nijenhuis,
personal information, 2007).
The correlation (r = 0.60) between the DES and the SDQ-20 (Study III) showed that
psychological and somatoform dissociation are to some extent overlapping constructs, and have
common features. Other studies have reported higher correlations of r = 0.76 (ùar et al., 2000),
r = 0.85 (Nijenhuis et al., 1999) and a similar correlation of r = 0.64 (El-Hage et al., 2002), but a
lower correlation (r = 0.51) has also been detected (Waller et al., 2000). These earlier studies have
81
usually been carried out on small and/or selected samples, which could explain the differences in
the results.
The use of cut-off scores to determine significant levels of dissociative experiences or to
distinguish dissociative disorders from other diagnostic categories has been examined in many
studies, but no unambiguous cut-off scores have been found. With higher cut-off scores the
possibility of missing positive cases increases, although the inclusion of false negatives decreases.
As our aim was to examine dissociative symptoms in the general population, we chose average cutoff scores to indicate high levels of dissociation on the grounds of the previous literature (Draijer
and Boon, 1993; Ross et al., 2002; ùar et al., 2000; Steinberg et al., 1991; Waller at al., 2001;
Waller and Ross, 1997).
Both the DES and the SDQ-20 are self-report measures. There are certain limitations to these
methods, mostly concerning the ability of individuals to evaluate and understand the meaning of the
items and the frequency of their occurrence in daily life. The DES was explicitly developed to be a
trait measure of dissociation. However, some individuals have scored very differently in our followup study, suggesting that individuals tend to give answers to the items on the basis of their
immediate past experiences.
6.8.3. Other measures
The reliability of the BDI (Cronbach’s alpha 0.89) and the TAS-20 (Cronbach’s alpha 0.86) has
previously been measured in this general population sample (Honkalampi et al., 2000, 2001).
Suicidal ideation was assessed with only one question from the BDI instead of a validated
questionnaire, and the results should therefore be considered with caution. Nevertheless, previous
studies have used the same method (Hintikka et al., 2001b) or a similar one (Gunnell et al., 2004) to
assess the presence of suicidal tendencies in general population samples.
Mental disorders diagnosed or treated by a physician were self-reported, and their accuracy was
not examined. However, it has been reported that there is usually no overestimation in this issue
(Aromaa et al., 1989). While all mental disorders were assessed in the original questionnaire, we
limited our Study IV to depression. Other comorbities may also affect the course of dissociative
symptoms, but they were not assessed in this study. The comorbidity of dissociative symptoms,
both psychological and somatoform, should be further examined.
82
7. Conclusions
7.1. Conclusions from the results
1) The prevalence of pathological dissociation in Finland was at the same level as in previous
studies in North America. There were no differences between genders in the prevalence of
pathological dissociation. Pathological dissociation was strongly associated with depressive
symptoms, suicidal ideation and alexithymia cross-sectionally.
2) Symptoms of somatoform dissociation were common in the general population, and high
somatoform dissociation was associated with male gender, an older age, a low level of education,
unemployment, a reduced working ability, and a poor financial situation. We found a graded,
positive relationship between an increasing number of adverse childhood experiences and high
somatoform dissociation. Factors associated with family pathology were also significant, providing
evidence of the complex issue of somatoform dissociation and adverse childhood experiences.
3) Those with both high psychological and high somatoform dissociation showed strong
comorbidity with depressive symptoms and suicidal ideation, and they were also disposed to
considerable adversities with their working ability, health and financial and social situation. The
correlation between DES and SDQ showed that psychological and somatoform dissociation are to
some extent overlapping constructs and have common features.
4) Only a small proportion of the general population suffered from constantly high levels of
dissociative symptoms. Among the stable high dissociators, significant comorbidity existed with
depressive symptoms and suicidal ideation. The stability of the dissociative taxon membership was
weaker than the stability of the continuous variables of dissociation.
7.2. Suggestions for future research
The stability of somatoform dissociation should be investigated and compared with the results
already obtained for the stability of psychological dissociation. Including trauma variables in the
study design would address the possible associations between both psychological and somatoform
dissociation and trauma in the general population. The factors associated with recovery from
83
dissociation in the general population require further research. The possible role of other comorbid
diagnostic categories in addition to depression should also be assessed.
The relationship between dissociation and alexithymia merits further study, taking into account
possible gender differences, the factor structure of alexithymia and possible associations with
somatoform dissociation.
7.3. Clinical implications
The comorbidity of dissociation with persistent depressive symptoms and chronic suicidal
ideation should be noted in clinical practice, especially among patients with a history of childhood
traumatization. Using self-report questionnaires (DES and SDQ-20) might be helpful in the
assessment of dissociative symptoms and disorders. A routine inquiry into dissociative symtoms of
the patient should be as important as the assessment of other psychiatric symptoms.
84
References
Acocella J. (1999) Creating hysteria: Women and Multiple Personality Disorder. San Francisco:
Jossey-Bass Publishers.
A÷argün M.Y., Tekeo÷lu I., Kara H., Adak B., Ercan M. (1998) Hypnotizability, pain threshold,
and dissociative experiences. Biological Psychiatry 44:69-71.
Akyüz G., Do÷an O., ùar V., Yargiç L.I., Tutkun H. (1999) Frequency of dissociative identity
disorder in the general population in Turkey. Comprehensive Psychiatry 40: 151-159.
Akyüz G., ùar V., Kugu N., Do÷an O. (2005) Reported childhood trauma, attempted suicide and
self-mutilative behavior among women in the general population. European Psychiatry 20:268-273.
Allen J.G., Fultz J., Huntoon J., Brethour J. R. (2002) Pathological dissociative taxon membership,
absorption, and reported childhood trauma in women with trauma-related disorders. Journal of
Trauma & Dissociation 3:89-110.
Altman D.G., Bland J.M. (1994) Quartiles, quintiles, centiles, and other quantiles. British Medical
Journal 309:996.
American Psychiatric Association (1994) Diagnostic and statistical manual of mental disorders,
Fourth Edition. DSM-IV. Washington, DC: American Psychiatric Association.
American Psychiatric Association (2000) Diagnostic and statistical manual of mental disorders,
Fourth Edition, Text revision. DSM-IV-TR. Washington, DC: American Psychiatric Association.
Anderson G., Yasenik L., Ross C.A. (1993) Dissociative experiences and dissociative disorders
among women who identify themselves as sexual abuse survivors. Child Abuse & Neglect 17:277686.
Armstrong J.G., Putnam F.W., Carlson E.B., Libero D.Z., Smith S.R. (1997) Development and
validation of a measure of adolescent dissociation: The adolescent dissociative experiences scale.
Journal of Nervous and Mental Disease 174:727-735.
Aromaa A., Heliövaara M., Impivaara O., Knekt P., Maatela J., Joukamaa M., Klaukka T., Lehtinen
V., Melkas T., Mälkiä E., Nyman K., Paunio I., Reunanen A., Sievers K., Kalimo E., Kallio V.
(1989) Health, functional limitations and need for care in Finland. Basic results from the MiniHealth Survey. AL:32, 793, Publications of the Social Insurance Institution, Helsinki and Turku,
Finland. [In Finnish with English summary]
Bagby R.M., Parker J.D.A., Taylor G.J. (1994) The twenty-item Toronto Alexithymia Scale-I: Item
selection and cross-validation of the factor structure. Journal of Psychosomatic Research 38:23-32.
Baker D., Hunter E., Lawrence E., Medford N., Patel M., Senior C., Sierra M., Lambert M.V.,
Phillips M.L., David A.S. (2003) Depersonalisation disorder: clinical features of 204 cases. British
Journal of Psychiatry 182:428-433.
Beck A.T., Steer R.A., Garbin M.G. (1988) Psychometric properties of the Beck Depression
Inventory. 25 years of evaluation. Clinical Psychology Review 8:77-100.
85
Beck A.T., Ward, C.H., Mendelson M., Mock J., Erbaugh J. (1961) An inventory for measuring
depression. Archives of General Psychiatry 4:561-571.
Becker-Blease K.A., Deater-Deckard K., Eley T., Freyd J.F., Stevenson J., Plomin R. (2004) A
genetic analysis of individual differences in dissociative behaviours in childhood and adolescence.
Journal of Child Psychology and Psychiatry 45:522-532.
Berenbaum H. (1996) Childhood abuse, alexithymia and personality disorder. Journal of
Psychosomatic Research 41:585-595.
Bernstein D.P., Fink L., Foote J., Lovejoy M., Wenzel K., Sapareto E., Ruggiero J. (1994) Initial
reliability and validity of a new retrospective measure of child abuse and neglect. American Journal
of Psychiatry 151:1132-1136.
Bernstein E.M., Putnam F.W. (1986) Development, reliability, and validity of a dissociation scale.
Journal of Nervous and Mental Disease 174:727-735.
Blizard R.A. (2003) Why was “dissociation” dissociated in psychoanalysis? Journal of Trauma &
Dissociation 4:1-5.
Boon S., Draijer N. (1993) Multiple personality disorder in the Netherlands: a clinical investigation
of 71 patients. American Journal of Psychiatry 150:489-494.
Bowins B. (2004) Psychological defence mechanisms: a new perspective. American Journal of
Psychonanalysis 64:1-26.
Bremner J.D., Krystal J.H., Charney D.S., Southwick S.M. (1996) Neural mechanisms in
dissociative amnesia for childhood abuse: relevance to the current controversy surrounding the
“False memory syndrome”. American Journal of Psychiatry 153:71-82.
Bremner J.D., Randall P., Vermetten E., Staib L., Bronen R.A., Mazure C., Capelli S., McCarthy
G., Innis R.B., Charney D.S. (1997) Magnetic resonance imaging-based measurement of
hippocampal volume in posttraumatic stress disorder related to childhood physical and sexual
abuse: a preliminary report. Biological Psychiatry 41:23-32.
Bremner J.D., Vythilingham M., Vermetten E., Southwick S.M., McGlashan T., Nazeer A., Khan
S., Vaccarino L.V., Soufer R., Garg P.K., Ng C.K., Staib L.H., Duncan J.S., Charney D.S. (2003)
MRI and PET study on deficits in hippocampal structure and function in women with childhood
sexual abuse and posttraumatic stress disorder. American Journal of Psychiatry 160:924-932.
Breslau N., Davis G.N., Schultz L.R. (2003) Posttraumatic stress disorder and the incidence of
nicotine, alcohol, and other drug disorders in persons who have experienced trauma. Archives of
General Psychiatry 60:289-294.
Breuer J., Freud S. (1955) Studies on hysteria. In J. Strachey & A. Strachey (eds.), Standard edition
of the complete psychological works of Sigmund Freud. London: Hogarth.
Buckley T.C., Holohan D.R., Mozley S.L., Walsh K., Kassel J (2007) The effect on nicotine and
attention allocation on physiological and self-report measures of induced anxiety in PTSD: a
double-blind placebo-controlled trial. Experimental and Clinical Psychopharmacology 15:154-164.
86
Butler L.D., Duran R.D.F., Jasiukaitis P., Koopman C., Spiegel D. (1996) Hypnotizability and
traumatic experience: A diathesis-stress model of dissociative symptomatology. American Journal
of Psychiatry 153:42-63.
Cardeña E., Nijenhuis E.R.S. (2000) Embodied sorrow: a special issue on somatoform dissociation.
Journal of Trauma & Dissociation 1:1-5.
Carlson E.B., Putnam F.W. (1989) Integrating research on dissociation and hypnotizability: are
there two pathways to hypnotizability? Dissociation 2:32-38.
Carlson E.B., Putnam F.W. (1993) An update on the Dissociative Experiences Scale. Dissociation
6:16-27.
Chu J, Bowman E. (2000) Trauma and Dissociation: 20 years of study and lessons learned along the
way. Journal of Trauma & Dissociation 1: 5-20.
Chu J.A., Dill D.L. (1990) Dissociative symptoms in relation to childhood physical and sexual
abuse. American Journal of Psychiatry 147:887-892.
Chu J.A., Frey L.M., Ganzel B.L., Matthews J.A. (1999) Memories of childhood abuse:
dissociation, amnesia, and corroboration. American Journal of Psychiatry 156:749-755.
Clayton K. (2004) The interrelatedness of dissociation: the relationship between dissociative
tendencies and alexithymia. Journal of Trauma & Dissociation 5:77-101.
Cloitre M., Scarvalone P., Difede J.A. (1997) Posttraumatic stress disorder, self- and interpersonal
dysfunction among sexually retraumatized women. Journal of Traumatic Stress 10:437-452.
Coons P.M., Bowman E.S. (2001) Ten-year follow-up study of patients with dissociative identity
disorder. Journal of Trauma & Dissociation 2:73-89.
Dell P.F. (2006a) The Multidimensional Inventory of Dissociation (MID): A comprehensive
measure of pathological dissociation. Journal of Trauma & Dissociation 7:77-106.
Dell P.F. (2006b) A new model of dissociative identity disorder. Psychiatric Clinics of North
America 29:1-26.
DePrince A.P., Cromer L. D. (2006) Introduction: Exploring Dissociation: Setting the Course.
Journal of Trauma & Dissociation 7:1-6.
DePrince A.P., Freyd J.J. (2004) Forgetting trauma stimuli. Psychological Science 15:488-492.
DeRuiter M.D., Elzinga B.M., Phaf R.H. (2006) Dissociation: capacity or dysfunction? Journal of
Trauma & Dissociation 7:115-134.
Diekstra R.F.W., Garnefski N. (1995) On the nature, magnitude, and causality of suicidal
behaviors: an international perspective. Suicide and Life-Threatening Behavior 25:36-57.
Donovan B.S., Padin-Rivera E., Dowd T., Blake D.D. (1996) Childhood factors and war zone stress
in chronic PTSD. Journal of Traumatic Stress 9:361-368.
87
Dorahy M.J. (2006) The dissociative processing style: a cognitive organization activated by
perceived or actual threat in clinical dissociators. Journal of Trauma & Dissociation 7:29-53.
Dorahy M.J., Van der Hart O. (2006) Fable or fact? Did Janet really come to repudiate his
dissociation theory? Journal of Trauma & Dissociation 7:29-37.
Draijer N., Boon S. (1993) The validation of the Dissociative Experiences Scale against the
criterion of the SCID-D, using receiver operating characteristics (ROC) analysis. Dissociation 7:2836.
Draijer N., Langeland W. (1999) Childhood trauma and perceived parental dysfunction in the
etiology of dissociative symptoms in psychiatric inpatients. American Journal of Psychiatry
156:379-385.
Driessen M., Hermann J., Stahl K., Zwaan M., Meier S., Hill A., Osterheider M., Petersen D.
(2000) Magnetic resonance imaging volumes of the hippocampus and amygdala in women with
borderline personality disorder and early traumatization. Archives of General Psychiatry 57:1151122.
Dube S.R., Anda R.F., Felitti V.J., Chapman D.P., Williamson D.F., Giles W.H. (2001) Childhood
abuse, household dysfunction, and the risk of attempted suicide throughout the life span. Findings
from the Adverse Childhood Experiences study. JAMA 286:3089-3096.
Dubester K.A., Braun B.G. (1995) Psychometric properties of the Dissociative Experience Scale.
Journal of Nervous Mental Disease 1995; 183:231-235.
El-Hage W., Darves-Bornoz J-M., Allilaire J-F., Gaillard P. (2002) Posttraumatic somatoform
dissociation in French psychiatric outpatients. Journal of Trauma & Dissociation 3:59-73.
Ellason J.W., Ross C.A. (1997) Two-year follow-up of inpatients with dissociative identity
disorder. American Journal of Psychiatry 154:842-839.
Ellason J.W., Ross C.A., Fuchs D.L. (1996) Life time axis I and axis II comorbidity and childhood
trauma history in dissociative identity disorder. Psychiatry 59:255-266.
Ellason J.W., Ross C.A., Mayran L.W., Sainton K. (1991) Convergent validity of the new form of
the DES. Dissociation 7:101-103.
Elzinga B.M., Bermond B., Van Dyck R. (2002) The relationship between dissociative proneness
and alexithymia. Psychotherapy and Psychosomatics 71:104-111.
Endo T., Sugiyama T., Someya T., (2006) Attention-deficit/hyperactivity disorder and dissociative
disorder among abused children. Psychiatry and Clinical Neurosciences 60:434-438.
Espirito Santo H.M., Pio-Abreu J.L. (2007) Dissociative disorders and other psychopathological
groups: exploring the difference through the somatoform dissociation questionnaire (SDQ-20).
Revista Brasileira de Psiquiatria 29:354-358.
Fahy T.A. (1988) The diagnosis of multiple personality disorder. A critical review. British Journal
of Psychiatry 153:597-606.
88
Fahy T.A., Abas M., Brown J.C. (1989) Multiple personality. A symptom of psychiatric disorder.
British Journal of Psychiatry 154:99-101.
Favazza A.R., Conterio K. (1988) The plight of chronic self-mutilators. Journal of Community
Mental Health 24:22-30.
Favazza A.R., Conterio K. (1989) Why patients mutilate themselves? Hospital and Community
Psychiatry 40:137-145.
Feldner M.T., Babson K.A., Zvolensky M.J., (2007) Smoking, traumatic event exposure, and posttraumatic stress: a critical review of the empirical literature. Clinical Psychology Review 27: 4–45.
Felitti V.J., Anda R.F., Nordenberg D., Williamson D.F., Spitz A.M., Edwards V., Koss M.P.,
Marks J.S. (1998) Relationship of childhood abuse and household dysfunction to many of the
leading causes of death in adults. The Adverse Childhood Experiences (ACE) study. American
Journal of Preventive Medine 14:245-258.
Fink P. (1996) From hysteria to somatisation: A historical perspective. Nordic Journal of Psychiatry
50: 353-363.
Flor-Henry P., Tomer R., Kumpula I., Koles Z.V., Yeudall L.T. (1990) Neurophysiological and
neuropsychological study of two cases of multiple personality syndrome and comparison with
chronic hysteria. International Journal of Psychophysiology 10:151-161.
Foote B., Smolin Y., Kaplan M., Legatt M.E., Lipschitz D. (2006) Prevalence of dissociative
disorders in psychiatric outpatients. American Journal of Psychiatry 163:623-629.
Francia-Martinez M., Roca de Torres I., Alvarado C.S., Martínez-Taboas A., Sayers S. (2003)
Dissociation, depression, and trauma in psychiatric inpatients in Puerto Rico. Journal of Trauma &
Dissociation 4:47-61.
Freyberger H. (1977) Supportive psychotherapeutic techniques in primary and secondary
alexithymia. Psychotherapy and Psychosomatics 28: 337-342.
Frischholz E.J., Braun B.G., Sachs R.G., Hopkins L., Schaeffer D.M., Lewis J., Leavitt F.,
Pasquotto J.N., Schwartz D.R. (1990) The Dissociative Experiences Scale: further replication and
validation. Dissociation 3:151-153.
Frischholz E.J., Lipman L.S., Braun B.G., Sachs R.G. (1992) Psychopathology, hypnotizability, and
dissociation. American Journal of Psychiatry 149:1521-1525.
Gershuny B.S., Thayer J.F. (1999) Relations among psychological trauma, dissociative phenomena,
and trauma-related distress. A review and integration. Clinical Psychology Review 19:631-657.
Gleaves D.H. (1996) The sociocognitive model of dissociative identity disorder: a re-examination
of the evidence. Psychological Bulletin 120:42-59.
Gleaves D.H., Williams T.L., Harrison K., Cororve M.B. (2000) Measuring dissociative
experiences in a college population: a study of convergent and discriminant validity. Journal of
Trauma & Dissociation 1:43-57.
89
Grabe H.-J., Rainermann S., Spitzer C., Gänsicke M., Freyberger H.J. (2000) The relationships
between dimensions of alexithymia and dissociation. Psychotherapy and Psychosomatics 69:128131.
Gunnell D., Harbord R., Singleton N., Jenkins R., Lewis G. (2004) Factors influencing the
development and amelioration of suicidal thoughts. Cohort study. British Journal of Psychiatry
185:385-393.
Haatainen K.M., Tanskanen A., Kylmä J., Honkalampi K., Koivumaa-Honkanen H., Hintikka J.,
Antikainen R., Viinamäki H. (2003) Gender differences in the association of adult hopelessness
with adverse childhood experiences. Social Psychiatry and Psychiatric Epidemiology 38:12-17.
Haule J. R. (1986) Pierre Janet and dissociation: The first transference theory and its origins in
hypnosis. American Journal of Clinical Hypnosis 29:86-94.
Haviland M.G., Reise S.P. (1996) A California Q-set alexithymia prototype and its relationship to
ego-control and ego-resiliency. Journal of Psychosomatic Research 41:597:608.
Herman J.L. (1992) Trauma and recovery. New York: Basic Books.
Higgins D.J., McCabe M.P. (2001) Multiple forms of child abuse and neglect: adult retrospective
reports. Aggression and Violent Behaviour 6:547-578.
Hilgard E.R. (1974) Toward a neodissociation theory: Multiple cognitive controls in human
functioning. Perspectives in Biology and Medicine 17:301-316.
Hilgard E.R. (1984) The hidden observer and multiple personality. The International Journal of
Clinical and Experimental Hypnosis XXXII: 248-253.
Hintikka J., Honkalampi K., Lehtonen J., Viinamäki H. (2001b) Are alexithymia and depression
distinct or overlapping constructs? A study in a general population. Comprehensive Psychiatry
42:234-239.
Hintikka J., Pesonen T., Saarinen P., Tanskanen A., Lehtonen J., Viinamäki H. (2001a) Suicidal
ideation in the Finnish general population. A 12-month follow-up study. Social Psychiatry and
Psychiatric Epidemiology 36:590-594.
Honkalampi K., Koivumaa-Honkanen H., Antikainen R., Haatainen K., Hintikka J., Viinamäki H.
(2004) Relationships among alexithymia, adverse childhood experiences, sociodemographic
variables, and actual mood disorder: a 2-year clinical follow-up study of patients with major
depressive disorder. Psychosomatics 45:197-204.
Honkalampi K., Koivumaa-Honkanen H., Tanskanen A., Hintikka J., Lehtonen J., Viinamäki H.
(2000) Depression in strongly associated with alexithymia in the general population. Journal of
Psychosomatic Research 48:99-104.
Honkalampi K., Koivumaa-Honkanen H., Tanskanen A., Hintikka J., Lehtonen J., Viinamäki H.
(2001) Why do alexithymic features appear to be stable? A 12-month follow-up study of a general
population. Psychotherapy and Psychosomatics 70: 247-253.
90
Irwin H.J. (1994) Proneness to dissociation and traumatic childhood events. Journal of Nervous and
Mental Disease 182:456-460.
Irwin H.J. (1999) Pathological and nonpathological dissociation: the relevance of childhood trauma.
Journal of Psychology 133:157-164.
Irwin H.J., Melbin-Helberg E.B. (1997) Alexithymia and dissociative tendencies. Journal of
Clinical Psychology 53: 159-166.
Jang K.L., Paris J., Zweig-Frank H., Livesley W.J. (1998) Twin study of dissociative experience.
Journal of Nervous and Mental Disease 186:345-351.
Joukamaa M., Miettunen J., Kokkonen P., Koskinen M., Julkunen J., Kauhanen J., Jokelainen J.,
Veijola J., Läksy K., Järvelin M.R. (2001) Psychometric properties of the Finnish 20-item Toronto
Alexithymia Scale. Nordic Journal of Psychiatry 55: 123-127.
Kampman R (1973) Hypnotically induced multiple personality. Acta Universitatis Ouluensis Series
D. Medica 6.
Kessler R.C., Borges G., Walters E.E. (1999) Prevalence of and risk factors for lifetime suicide
attempts in the National Comorbidity Survey. Archives of General Psychiatry 56:617-626.
Kisiel C.L., Lyons J.S. (2001) Dissociation as a mediator of psychopathology among sexually
abused children and adolescents. American Journal of Psychiatry 158:1034-1039.
Kluft R.P. (1984) An introduction to multiple personality disorder. Psychiatric Annals 14:19-24.
Lee G.P., Bechara A., Adolphs R., Arena J., Meador K.J., Loring D.W., Smith J.R. (1998) Clinical
and physiological effects of stereotaxic bilateral amygdalotomy for intractable aggression. Journal
of Neuropsychiatry and Clinical Neuroscience 10:413-420.
Lipsanen T. (2004) Dissociation as a psychiatric phenomenon. Annales Universitatis Turkuensis.
SER. D. TOM. 615. Medica – Odontologica.
Lipsanen T., Korkeila J., Peltola P., Järvinen J., Langen K., Lauerma H. (2004a) Dissociative
disorders among psychiatric patients. European Psychiatry 19:53-55.
Lipsanen T., Lauerma H., Peltola P., Kallio S. (2000) Associations among dissociative experiences,
handedness, and demographic variables in a nonclinical population. Journal of Nervous and Mental
Disease 188:422-427.
Lipsanen T., Lauerma H., Peltola P., Kallio S. (1999) Visual distorsions and dissociation. Journal of
Nervous and Mental Disease 187:109-112.
Lipsanen T., Saarijärvi S., Lauerma H. (2003) The Finnish version of the Dissociative Experiences
Scale-II (DES-II) and psychiatric distress. Nordic Journal of Psychiatry 57:17-22.
Lipsanen T., Saarijärvi S., Lauerma H. (2004b) Exploring the relations between depression,
somatization, dissociation and alexithymia – overlapping or independent constructs?
Psychopathology 37:200-206.
91
Lochner C., Seedat, S., Hemmings S. M. J., Moolman-Smook, J. C., Kidd, M., Stein D.J. (2007)
Investigating the possible effects of trauma experiences and the 5-HTT on the dissociative
experiences of patients with OCD using path analysis and multiple regression. Neuropsychobiology
56:6-13.
Low G., Jones D., MacLeod A., Power M., Duggan C. (2000) Childhood trauma, dissociation, and
self-harming behavior: A pilot study. British Journal of Medical Psychology 73:269-278.
Mathew R.J., Jack R.A., West W.S. (1985) Regional cerebral blood flow in a patient with multiple
personality disorder. American Journal of Psychiatry 142:504-505.
Matsumoto T., Imamura F. (2007) Association between childhood attention-deficit-hyperactivity
symptoms and adulthood dissociation in male inmates: Preliminary report. Psychiatry and Clinical
Neurosciences 61:444-446.
Matsumoto T., Yamagushi A., Asami T., Okada T., Yoshikawa K., Hirayasu Y. (2005)
Characteristics of self-cutters among male inmates: association with bulimia and dissociation.
Psychiatry and Clinical Neurosciences 59:319-326.
McNally R.J. (2007) Dispelling confusion about traumatic dissociative amnesia. Mayo Clinic
Proceedings 82:1083-1087.
McNally R.J., Ristuccia C.S., Perlman C.A. (2005) Forgetting of trauma cues in adults reporting
continuous or recovered memories of childhood sexual abuse. Psychological Science 16:336-340.
McWilliams N. (1994) Psychoanalytic diagnosis: understanding personality structure in clinical
process. New York, NY: Guilford Press.
Meyers, C.S. (1916a) Contributions to the study of shell shock. The Lancet, 608-613.
Meyers, C.S. (1916b) Contributions to the study of shell shock. The Lancet, 461-467.
Modestin J., Erni T. (2004) Testing the dissociative taxon. Psychiatry Research 126:77-82.
Modestin J., Lötscher K., Erni T. (2002) Dissociative experiences and their correlates in young nonpatients. Psychology and Psychotherapy: Theory, Research and Practice 75:53-64.
Mulder R.T., Beautrais A.L., Joyce P.R., Fergusson D.M. (1998) Relationship between dissociation,
childhood sexual abuse, childhood physical abuse, and mental illness in a general population
sample. American Journal of Psychiatry 155:806-811.
National Research and Development Centre for Welfare and Health. Statistics 2001.
Nemiah J.C. (1977) Alexithymia. Theoretical considerations. Psychotherapy and Psychosomatics
28:199-206.
Nemiah J.C. (1991) Dissociation, conversion, and somatization. American Psychiatric Press Review
of Psychiatry, vol 10:248-260.Tasman A., Goldfinger S.M. (Eds). Washington DC, American
Psychiatric Press.
92
Nemiah J.C. (2000) A psychodynamic view of psychodynamic medicine. Psychosomatic Medicine
62:299-303.
Nijenhuis E.R.S. (2000) Somatoform dissociation: major symptoms of dissociative disorders.
Journal of Trauma & Dissociation 1:7-29.
Nijenhuis E.R.S. (2004) Somatoform dissociation. Phenomena, measurement, and theoretical
issues. W.W. Norton & Company, Inc., 500 Fifth Avenue, New York, N.Y. 10110.
Nijenhuis E.R.S., Spinhoven P., Vanderlinden J., Van Dyck R., Van der Hart O. (1998b)
Somatoform dissociative symptoms as related to animal defensive reactions to predatory imminence
and injury. Journal of Abnormal Psychology 107:63-73.
Nijenhuis E.R.S., Spinhoven P., Van Dyck R., Van der Hart O., Vanderlinden J. (1996) The
development and psychometric characteristics of the Somatoform Dissociation Questionnaire
(SDQ-20). Journal of Nervous and Mental Disease 184:688-694.
Nijenhuis E.R.S., Spinhoven P., Van Dyck R., Van der Hart O., Vanderlinden J. (1997) The
development of the somatoform dissociation questionnaire (SDQ-5) as a screening instrument for
dissociative disorders. Acta Psychiatrica Scandinavica 96:311-318.
Nijenhuis E.R.S., Spinhoven P., Van Dyck R., Van der Hart O., Vanderlinden J. (1998a)
Psychometric characteristics of the Somatoform Dissociation Questionnaire: a replication study.
Psychotherapy and Psychosomatics 67:17-23.
Nijenhuis E.R.S., Spinhoven P., Van Dyck R., Van der Hart O., Vanderlinden J. (1998c) Degree of
somatoform and psychological dissociation in dissociative disorder is correlated with reported
trauma. Journal of Traumatic Stress 11:711-730.
Nijenhuis E.R.S., Van der Hart O., Kruger K., Steele K. (2004) Somatoform dissociation, reported
abuse and animal defence-like reactions. Australian and New Zealand Journal of Psychiatry 38:678686.
Nijenhuis E.R.S., Van Dyck R., Spinhoven P., Van der Hart O., Chatrou M., Vanderlinden J.,
Moene F. (1999) Somatoform dissociation discriminates among diagnostic categories over and
above general psychopathology. Australian and New Zealand Journal of Psychiatry 33:511-520.
Nijenhuis E.R.S., Van Dyck R., Ter Kuile M.M., Mourits M.J.E., Spinhoven P., Van der Hard O.
(2003) Evidence for associations among somatoform dissociation, psychological dissociation and
reported trauma in patients with chronic pelvic pain. Journal of Psychosomatic Obstetrics &
Gynecology 24:87-98.
Nijenhuis E., Van Engen A., Kusters I., Van der Hart O. (2001) Peritraumatic somatoform and
psychological dissociation in relation to recall of childhood sexual abuse. Journal of Trauma &
Dissociation 2:49-68.
Näring G, Nijenhuis E.R.S. (2005) Relationships between self-reported potentially traumatizing
events, psychoform and somatoform dissociation, and absorption, in two non-clinical populations.
Australian and New Zealand Journal of Psychiatry 39:982-988.
93
Pattison E.M., Kahan J. (1983) The deliberate self-harm syndrome. American Journal of Psychiatry
140:867-872.
Putnam F.W. (1989) Diagnosis and treatment of multiple personality disorder. The Guilford Press,
New York.
Putnam F.W., Carlson E.B., Chu J.A., Dill D.L. (1992) “The Dissociative Experiences Scale”:
Reply. American Journal of Psychiatry 149:143-144.
Putnam F.W., Carlson E.B., Ross C.A., Anderson G., Clark P., Torem M., Bowman E.S., Coons P.,
Chu J.A., Dill D.L., Loewenstein R.J., Braun B.G. (1996) Patterns of dissociation in clinical and
nonclinical samples. Journal of Nervous and Mental Disease 184:673-679.
Rauch S.L., Van der Kolk B.A., Fisler R.E., Alpert N.M., Orr S.P., Savage C.R., Fischman A.J.,
Jenike M.A., Pitman R.K. (1996) A symptom provocation study of posttraumatic stress disorder
using positron emission tomography and script-driven imagery. Archives of General Psychiatry
53:380-387.
Rieber R.W. (2002) The duality of the brain and the multiplicity of minds: can you have it both
ways? History of Psychiatry 13:3-17.
Roelofs K., Keijsers G.P.J., Hoogduin K.A.L., Näring G.W.B., Moene F.C. (2002) Childhood abuse
in patients with conversion disorder. American Journal of Psychiatry 159:1908-1913.
Ross C.A., Anderson G., Fleisher W.P., Norton G.R. (1991) The frequency of multiple personality
disorder among psychiatric inpatients. American Journal of Psychiatry 148:1717-1720.
Ross C.A., Duffy C.M.M., Ellason J.W. (2002) Prevalence, reliability and validity of dissociative
disorders in an inpatient setting. Journal of Trauma & Dissociation 3:7-17.
Ross C.A., Ellason J.W (2005) Discriminating among diagnostic categories using the Dissociative
Disorders Interview Schedule. Psychological Reports 96:445-453.
Ross C.A., Heber S., Norton G.R., Anderson G. (1989) Differences between multiple personality
disorder and other diagnostic groups on structured interview. Journal of Nervous and Mental
Disease 177: 487-491.
Ross C.A., Joshi S., Currie R. (1990) Dissociative experiences in the general population. American
Journal of Psychiatry 147: 1547-1552.
ùar V. (2006) The scope of dissociative disorders: an international perspective. Psychiatric Clinics
of North America 29:227-244.
ùar V., Akyüz G., Do÷an O. (2007) Prevalence of dissociative disorders among women in the
general population. Psychiatry Research 149:169-176.
ùar V., Akyüz G., KundakçȚ T., KȚzȚltan E., Do÷an O. (2004) Childhood trauma, dissociation, and
psychiatric comorbidity in patients with conversion disorder. American Journal of Psychiatry
161:2271-2276.
94
ùar V., KundakçȚ T., KȚzȚltan E., Bakim B., Bozkurt O. (2000) Differentiating dissociative disorders
from other diagnostic groups through somatoform dissociation in Turkey. Journal of Trauma &
Dissociation 1:67-80.
ùar V., Unal S.N., KȚzȚltan E., KundakçȚ T., Ozturk E. (2001) HMPAO SPECT study of regional
cerebral blood flow in dissociative identity disorder. Journal of Trauma & Dissociation 2:5-25.
Saxe G.N., Chawla N., Van der Kolk B.A. (2002) Self-destructive behavior in patients with
dissociative disorders. Suicide and Life-Threatening Behavior 32:313-320.
Saxe G.N., Van der Kolk B.A., Berkowitz R., Chinman G., Hall K., Lieberg G., Schwartz J. (1993)
Dissociative disorders in psychiatric inpatients. American Journal of Psychiatry 150:1037-1042.
Saxe G.N., Vasile R.G., Hill T.C., Bloomingsdale K., Van der Kolk B.A. (1992) SPECT imaging
and multiple personality disorder. Journal of Nervous and Mental Disease 180:662-663.
Schäfer I., Reininghaus U, Langeland W, Voss A., Zieger N, Haasen C, Karow A. (2007)
Dissociative symptoms in alcohol-dependant patients: associations with childhood trauma and
substance abuse characteristics. Comprehensive Psychiatry 48:539-545.
Seedat S., Stein M.B., Forde D.R. (2003) Prevalence of dissociative experiences in the community
sample. Relationship to gender, ethnicity, and substance use. Journal of Nervous and Mental
Disease 191:115-120.
Sifneos P.E. (1973) The prevalence of “alexithymic” characteristics in psychosomatic patients.
Psychotherapy and Psychosomatics 22: 55-262.
Simeon D., Knutelska M., Nelson D., Guralnik O., Schmeidler J. (2003) Examination of the
pathological dissociation taxon in depersonalization disorder. Journal of Nervous and Mental
Disease 191:738-744.
Spanos N.P. (1994) Multiple identity enactments and multiple personality disorder: a sociocognitive
perspective. Psychological Bulletin 116:143-165.
Spiegel D., Hunt D., Dondershine H.E. (1988) Dissociation and hypnotizability in posttraumatic
stress disorder. American Journal of Psychiatry145:301-305.
Spitzer C., Barnow S., Grabe H.J., Klauer T., Stieglitz R.D., Scheiner W., Freyberger H.J. (2006)
Frequency, clinical and demographic correlates of pathological dissociation in Europe. Journal of
Trauma & Dissociation 7:51-62.
Spitzer C., Freyberger H.J., Stieglitz R.-D., Carlson E.B., Kuhn G., Magdeburg N., Kessler C.
(1998) Adaptation and psychometric properties of the German version of the Dissociative
Experiences Scale. Journal of Traumatic Stress 11:799-809.
Spitzer C, Klauer T, Grabe HJ, Lucht M, Stieglitz RD, Scheiner W, Freyberger HJ (2003) Gender
differences in dissociation. A dimensional approach. Psychopathology 36: 65-70.
Steinberg M. (1994) Systematizing dissociation: symptomatology and diagnostic assessment. In D.
Spiegel (Ed.), Dissociation: culture, mind, and body. American Psychiatric Publishing.
95
Steinberg M., Cicchetti D., Buchanan J., Hall P., Rounsaville B. (1993) Clinical assessment of
dissociative symptoms and disorders: the structured clinical interview for DSM-IV dissociative
disorders (SCID-D). Dissociation 6:3-15.
Steinberg M., Rounsaville B., Cicchetti D. (1991) Detection of dissociative disorders in psychiatric
patients by a screening instrument and a structured diagnostic interview. American Journal of
Psychiatry 148:1050-1054.
Tanskanen A. (1997) Dissociative Experiences Scale, DES II. Finnish version.
http://www.sidran.org/store/index.cfm?fuseaction=product.display&Product_ID=62 17.7.2008
Taylor G.J. (1994) The alexithymia construct: conceptualization, validation, and relationships with
basic dimensions of personality. New Trends in Experimental and Clinical Psychiatry 10:61-74.
Taylor G.J. (2000) Recent developments in alexithymia theory and research. Canadian Journal of
Psychiatry 45:134-142.
Taylor G.J., Bagby R.M., Parker J.D.A. (1997) Disorders of affect regulation. Cambridge:
Cambridge University Press.
Teicher M.H., Anderson S.L., Polcari A., Anderson C.M., Navalta C.P. (2002) Developmental
neurobiology of childhood stress and trauma. Psychiatric Clinics of North America 25:397-426.
Teicher M.H., Samson J.A., Polcari A., McGreenery C.E. (2006) Sticks, stones, and hurtful words:
relative effects of various forms of childhood maltreatment. American Journal of Psychiatry
163:993-1000.
Terzan E., Atmaca M., Kologlu M., Gecici O., Buyukbayram A., Tutkun H. (1998) Dissociative
disorders in Turkish inpatients with conversion disorder. Comprehensive Psychiatry 44:324-330.
Tiihonen J., Kuikka J., Viinamäki H., Lehtonen J., Partanen J. (1995) Altered cerebral blood flow
during hysterical paresthesia. Biological Psychiatry 37:134-137.
Tolmunen T., Maaranen P., Hintikka J, Kylmä J., Rissanen M.-L., Honkalampi K., Haukijärvi T.,
Laukkanen E. (2007) Dissociation in a general population of Finnish Adolescents. Journal of
Nervous and Mental Disease 195:614-617.
Tutkun H., ùar V., Yargic L.I., Ozpulat T., Yanik M., KȚzȚltan E. (1998) Frequency of dissociative
disorders among psychiatric inpatients in a Turkish university clinic. American Journal of
Psychiatry 155:800-805.
Tutkun H., Savas H.A., Zoroglu S.S., Eski K., Herken H., Tiryaki N. (2004) Relationship between
alexithymia, dissociation and anxiety in psychiatric outpatients from Turkey. Israel Journal of
Psychiatry and Related Science 41:118-124.
Van der Hart O., Bolt H., Van der Kolk B.A. (2005) Memory fragmentation and dissociative
identity disorder. Journal of Trauma & Dissociation 6:55-69.
Van der Hart O., Friedman B. (1989) A reader’s guide to Pierre Janet on dissociation: A neglected
intellectual heritage. Dissociation 2:3-16.
96
Van der Hart O., Horst R. (1989) The dissociation theory of Pierre Janet. Journal of Traumatic
Stress 2:397-412.
Van der Hart O., Nijenhuis E.R.S., Steele K. (2006) The Haunted Self. Structural dissociation and
the treatment of chronic traumatization. W.W. Norton & Company, Inc., 500 Fifth Avenue, New
York, N.Y., 10110.
Van der Hart O., Van Dijke A., Van Son M., Steele K. (2000) Somatoform dissociation in
traumatized World War I combat soldiers: a neglected clinical heritage. Journal of Trauma &
Dissociation 1:33-66.
Van der Kolk B.A., Pelcovitz D., Roth S., Mandel F.S., McFarlane A., Herman J.L. (1996)
Dissociation, somatization, and affect dysregulation: the complexity of adaptation to trauma.
American Journal of Psychiatry 153:83-93.
Vanderlinden J., Van Dyck R., Vandereycken W., Vertommen H. (1991) Dissociative experiences
in the general population in the Netherlands and Belgium. Dissociation 4: 180-184.
Vanderlinden J., Van Dyck R., Vandereycken W., Vertommen H. (1993) Dissociation and
traumatic experiences in the general population of the Netherlands. Hospital and Community
Psychiatry 44:786-788.
Van der Velden P.G., Grievink L., Olff M., Gersons B.P., Kleber R.J., Dutch Ministry of Health,
Welfare, and Sport (2007) Smoking as a risk factor for mental health disturbances after a disaster: a
prospective comparative study. Clinical Journal of Psychiatry 68:87-92.
Van Ijzendoorn M.H., Schuengel C. (1996) The measurement of dissociation in normal and clinical
populations: Meta-analytic validation of the dissociative experiences scale (DES). Clinical
Psychology Review 16:365-382.
Vermetten E., Schmahl C., Lindner S., Loewenstein R.J., Bremner J.D. (2006) Hippocampal and
amygdalar volumes in dissociative identity disorder. American Journal of Psychiatry 163:630-636.
Vythilingham M., Heim C., Newport J., Miller A.H., Anderson E., Bronen R., Brummer M., Staib
L., Vermetten E., Charney D.S. (2002) Childhood trauma associated with smaller hippocampal
volume in women with major depressive disorder. American Journal of Psychiatry 159:2072-2080.
Waller G., Hamilton K., Elliott P., Lewendon J., Stopa L., Waters A., Kennedy F., Lee G., Pearson
D., Kennerley H., Hargreaves I., Bashford V., Chalkley J. (2000) Somatoform dissociation,
psychological dissociation, and specific forms of trauma. Journal of Trauma & Dissociation 1:8198.
Waller G., Ohanian V., Meyer C., Everill J., Rouse H. (2001) The utility of dimensional and
categorical approaches to understanding dissociation in the eating disorders. British Journal of
Clinical Psychology 40: 387-397.
Waller N.G., Putnam F.W., Carlson E.B. (1996) Types of dissociation and dissociative types: A
taxometric analysis of dissociative experiences. Psychological Methods 1: 300-321.
97
Waller N.G., Ross C.A. (1997) The prevalence and biometric structure of pathological dissociation
in the general population: taxometric and behavior genetic findings. Journal of Abnormal
Psychology 106: 499-510.
Watson D. (2003) Investigating the construct validity of the dissociative taxon: stability analyses of
normal and pathological dissociation. Journal of Abnormal Psychology 112:298-305.
Wise T.N., Mann L.S., Sheridan M.J. (2000) Relationship between alexithymia, dissociation and
personality in psychiatric outpatients. Psychotherapy and Psychosomatics 69:123-127.
World Health Organization (1992) The ICD-10 Classification of mental and behavioral disorders:
Clinical description and diagnostic guidelines. Geneva: WHO.
Xiao Z., Yan H., Wang Z., Zou Z., Xu Y., Chen J., Zhang H., Ross C.A., Keyes B.B. (2006a)
Trauma and dissociation in China. American Journal of Psychiatry 163:1388-1391.
Xiao Z., Yan H., Wang Z., Zhou Z., Xu Y., Cheng J., Zhang H., Ross C.A., Keyes B.B. (2006b)
Dissociative experiences in China. Journal of Trauma & Dissociation 7:23-38.
Yargic L.I., ùar V., Tutkun H., Alanyak B. (1998) Comparison of dissociative identity disorder with
other diagnostic groups using a structured interview in Turkey. Comprehensive Psychiatry 39:345351.
Zoroglu S.S., Tuzun U., ùar V., Tutkun H., Savaú H.A., Ozturk M., Alyanak B., Kora M.E. (2003)
Suicide attempt and self-mutilation among Turkish high school students in relation with abuse,
neglect and dissociation. Psychiatry and Clinical Neuroscience 57: 119-126.
Appendix I
Dissociative Experiences Scale (DES)
Dissosiatiivisten kokemusten asteikko
Ohjeet:
Tässä kyselylomakkeessa on 28 kysymystä kokemuksista, joita Sinulla saattaa ilmetä
arkielämässäsi. Me olemme kiinnostuneita siitä, onko Sinulla, ja jos on, kuinka usein näitä
kokemuksia silloin, kun et ole alkoholin tai huumeiden vaikutuksen alaisena. Pyydämme Sinua
ystävällisesti vastaamaan kysymyksiin siten, että mietit, missä määrin kysymyksessä kuvailtu
kokemus sopii Sinuun, ja ympyröimään sitten sopivan numeron, joka ilmaisee, kuinka suuren osan
ajasta Sinulla on näitä kokemuksia.
Esimerkki:
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
© 1986: Originally published in English by Carlson EB & Putnam FW. All rights reserved.
© 1997: Suomentanut Antti Tanskanen, KYS, psykiatrian klinikka. Kaikki oikeudet pidätetään.
Varsinaiset kysymykset (1-28):
1. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan autoa (tai polkupyörää tms.) ajaessaan
tai ollessaan jonkin ajoneuvon (auton, bussin, junan tms.) kyydissä, että he eivät muista
mitään koko matkasta tai osasta matkaa.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
2. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan, että kuunnellessaan jonkun puhetta he
eivät ole kuulleet ollenkaan, tai ovat kuulleet vain osittain, mitä toinen puhui.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
3. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan olevansa jossakin paikassa, mutta heillä
ei ole aavistustakaan siitä, miten he sinne olivat tulleet.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
20
30
40
50
60
70
80
90
100 %
(ei koskaan)
(aina)
4. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan pukeutuneensa vaatteisiin, joita he eivät
muista pukeneensa ylleen.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
5. Jotkut ihmiset saattavat löytää tavaroidensa joukosta uusia esineitä, joita he eivät muista
ostaneensa.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
6. Jotkut ihmiset kohtaavat joskus vieraita ihmisiä, joita he eivät tunne ja jotka puhuttelevat
heitä toisella nimellä tai väittävät tavanneensa heidät aiemmin.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
7. Jotkut ihmiset kokevat joskus, että he tuntevat ikään kuin seisovansa itsensä vieressä tai
katselevansa omia tekemisiään ja he todella näkevät itsensä ikään kuin katselisivat jotakin
toista ihmistä.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
8. Joillekin ihmisille käy joskus niin, että heitä moititaan, koska he eivät tunne eivätkä
tervehdi omia ystäviään ja perheenjäseniään.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
9. Jotkut ihmiset kokevat, että he eivät muista lainkaan tärkeitä tapahtumia (esim. koulun
päättäjäisiä, häitä) omasta elämästään.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
10. Jotkut ihmiset kokevat, että heitä syytetään valehtelusta, vaikka he omasta mielestään
eivät ole valehdelleet.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
11. Jotkut ihmiset kokevat peiliin katsoessaan, että peilistä näkyvä kuva ei ole heidän oma
kuvansa.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
12. Jotkut ihmiset kokevat, että ihmiset, esineet ja maailma heidän ympärillään eivät ole
todellisia.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
13. Jotkut ihmiset kokevat, että heidän kehonsa ei tunnu omalta.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
14. Jotkut ihmiset muistavat joskus jonkin menneen tapahtuman niin elävästi, että tuntevat
ikään kuin elävänsä sen uudelleen.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
15. Jotkut ihmiset eivät ole varmoja siitä, ovatko tietyt asiat todella tapahtuneet niin kuin he
muistelevat vai onko kaikki ollut vain haaveilua tai unta.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
16. Jotkut ihmiset kokevat tutussa paikassa ollessaan, että tuo tuttu paikka on outo ja vieras.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
17. Jotkut ihmiset eläytyvät ja tempautuvat mukaan katsomaansa TV-ohjelmaan tai
elokuvaan niin täysin, etteivät he ole tietoisia ympäristön tapahtumista.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
18. Jotkut ihmiset huomaavat uppoavansa niin syvälle kuvitelmiinsa tai haaveisiinsa, että
heistä tuntuu siltä, kuin nuo asiat todellisuudessa tapahtuisivat heille.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
19. Jotkut ihmiset huomaavat pystyvänsä joskus olemaan kiinnittämättä huomiota kipuun.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
20. Jotkut ihmiset löytävät itsensä joskus tuijottamasta tyhjyyteen, niin että he eivät ajattele
mitään eivätkä huomaa ajan kulumista.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
21. Jotkut ihmiset huomaavat joskus yksin ollessaan puhuvansa ääneen itselleen.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
22. Jotkut ihmiset kokevat, että he saattavat toimia hyvin eri tavalla jossakin tilanteessa kuin
jossakin toisessa tilanteessa. Heistä tuntuu, ikään kuin he olisivat noissa eri tilanteissa kaksi
eri ihmistä.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
23. Jotkut ihmiset kokevat joskus, että he tietyissä tilanteissa (esim. urheilussa, työssä,
juhlissa, asioimistilanteissa, muiden kanssa keskustellessaan tai seurustellessaan, jne.)
pystyvät tekemään tiettyjä asioita hämmästyttävän helposti ja vaistomaisesti, vaikka ne
tavallisesti olisivat heille vaikeita.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
24. Jotkut ihmiset kokevat joskus, että he eivät voi muistaa, ovatko he todella tehneet jonkin
asian vai ovatko he vain ajatelleet tehneensä sen (esim. eivät muista, ovatko postittaneet
kirjeen tai vain ajatelleet postittaneensa sen).
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
25. Jotkut ihmiset löytävät todisteita siitä, että he ovat tehneet jotakin, mitä he eivät muista
tehneensä.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
26. Jotkut ihmiset löytävät joskus tavaroidensa joukosta kirjoituksia, piirustuksia tai
muistiinpanoja, jotka heidän on täytynyt tehdä mutta joita he eivät voi muistaa tehneensä.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
27. Jotkut ihmiset huomaavat joskus kuulevansa päänsä sisältä ääniä, jotka kehottavat heitä
tekemään jotain tai ottavat kantaa siihen, mitä he tekevät.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
28. Joistakin ihmisistä tuntuu joskus siltä, että he ikään kuin katselevat maailmaa
sumuverhon läpi, niin että ihmiset ja esineet näyttävät olevan kaukana tai epäselviä.
Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.
0%
10
(ei koskaan)
20
30
40
50
60
70
80
90
100 %
(aina)
Appendix II
Somatoform Dissociation Questionnaire (SDQ-20)
Somatoformisen dissosiaation mittari
Seuraava kysymyssarja käsittelee kokemuksia, joita joillakin ihmisillä voi olla joskus. Ympyröikää
jokaisen kysymyksen kohdalla jokin numeroista 1-5.
1 = ei sovi minulle lainkaan
2 = saattaa sopia minulle
3 = sopii minulle
4 = sopii minulle hyvin
5 = sopii minulle erinomaisesti
ei sovi minulle
lainkaan
1. On niin, että ikään kuin kehoni, tai osa siitä,
olisi kadonnut.
2. Olen halvaantunut jonkin aikaa.
3. En voi puhua (tai vain suurin ponnistuksin),
tai voin vain kuiskata.
4. Kehoni, tai osa siitä, on tunnoton kivulle.
5. Tunnen virtsatessa kipua.
6. Jonkin aikaa on niin, etten voi nähdä (ikään
kuin olisin sokea)
7. Minulla on virtsaamisvaikeuksia.
8. Jonkin aikaa on niin, etten voi kuulla (ikään
kuin olisin kuuro)
9. Kuulen läheltä tulevat äänet niin, ikään kuin
ne tulisivat kaukaa.
10. Jäykistyn hetkeksi.
11. Minulla ei ole flunssaa, mutta silti pystyn
haistamaan paljon paremmin tai huonommin
kuin tavallisesti.
12. Tunnen kipua sukupuolielimissäni (muulloin
kuin yhdynnässä).
13. Minulla on kohtaus, joka muistuttaa
epileptistä kohtausta.
14. Tunnen vastenmielisyyttä tuoksuihin, joista
yleensä pidän.
15. Tunnen vastenmielisyyttä makuihin, joista
yleensä pidän (naisilla muulloin kuin
raskauden ja kuukautisten aikana).
16. Näen esineet ympärilläni eri tavalla kuin
yleensä (esim. ikään kuin katselisin tunnelin
läpi tai näkisin vain osan kohteesta).
17. En voi nukkua öitäni loppuun saakka, mutta
pysyn hyvin aktiivisena päiväsaikaan.
18. En voi niellä, tai vain suurin ponnistuksin.
19. Ihmiset ja esineet näyttävät suuremmilta
kuin ne todellisuudessa ovat.
20. Kehoni, tai osa siitä, tuntuu puutuneelta.
sopii minulle
sopii minulle
erinomaisesti
1
1
2
2
3
3
4
4
5
5
1
1
1
2
2
2
3
3
3
4
4
4
5
5
5
1
1
2
2
3
3
4
4
5
5
1
2
3
4
5
1
1
2
2
3
3
4
4
5
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
1
2
2
3
3
4
4
5
5
1
2
3
4
5
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