Download The substance

Dipl.-Psych. Roland Simon
Tel. 089 / 360804 - 40
Fax 089 / 360804 - 49
e-mail: [email protected]
30.3.2004
Project:
Regular and intensive use of cannabis and related problems:
conceptual framework and data analysis in the EU member states
Final Report
CT.2003.103.P1
D:\747141584.doc 30.3.2004
CONTENTS
1
Introduction ............................................................................................................1
1.1
Background.............................................................................................................................. 1
1.2
The project ............................................................................................................................... 1
1.3
Implementation ........................................................................................................................ 2
2
Assessment tools and instruments ......................................................................3
2.1
Assessing problem cannabis use through patterns of use ...................................................... 3
2.2
Assessing problem cannabis use through clinical aspects of use .......................................... 3
CIDI .......................................................................................................................................... 3
CRAFFT ................................................................................................................................... 4
CUDIT ...................................................................................................................................... 4
EuropASI ................................................................................................................................. 4
MECA ...................................................................................................................................... 5
SDS ......................................................................................................................................... 5
2.3
Conclusions ............................................................................................................................. 5
3
The substance ........................................................................................................6
3.1
Availability and illegal market .................................................................................................. 6
Availability and drug use .......................................................................................................... 6
Perceived availability ............................................................................................................... 6
Drug market ............................................................................................................................. 6
Other ways to assess availability............................................................................................. 7
3.2
Purity ........................................................................................................................................ 8
Trends in purity ........................................................................................................................ 8
Effects of increased purity ....................................................................................................... 8
4
Problematic use of cannabis ..............................................................................10
4.1
4.1.1
4.1.2
4.1.3
4.1.4
Antecedents of problem cannabis use .................................................................................. 10
Demographic factors ............................................................................................................. 11
Family background and social situation ................................................................................ 11
Use of other psychotropic substances .................................................................................. 12
Mental disorders and problems ............................................................................................. 12
4.2
4.2.1
4.2.2
Acute Effects.......................................................................................................................... 12
Overview ................................................................................................................................ 12
Somatic effects ...................................................................................................................... 13
Intoxication............................................................................................................................. 13
Mortality ................................................................................................................................. 13
Cardiovascular effects ........................................................................................................... 13
Respiratory system ................................................................................................................ 14
Psychomotor effects .............................................................................................................. 14
Other somatic effects ............................................................................................................. 14
Mental effects ........................................................................................................................ 14
Cognition ................................................................................................................................ 14
Dysphoria, anxiety and panic disorders ................................................................................ 14
Toxic psychoses .................................................................................................................... 15
4.2.3
4.3
4.3.1
4.3.2
Chronic Effects ...................................................................................................................... 15
Overview ................................................................................................................................ 15
Somatic effects ...................................................................................................................... 15
Respiratory system ................................................................................................................ 15
Reproduction ......................................................................................................................... 16
Other somatic effects ............................................................................................................. 16
ii
4.3.3
Mental effects ........................................................................................................................ 16
Cognition ................................................................................................................................ 17
Development.......................................................................................................................... 18
Depression and suicide ......................................................................................................... 19
Schizophrenia ........................................................................................................................ 19
Tolerance syndrome, harmful use and addiction .................................................................. 21
Use of other psychotropic substances .................................................................................. 22
4.4
4.4.1
4.4.2
4.4.3
Secondary Effects.................................................................................................................. 23
Effects to unborn children ...................................................................................................... 23
Performance and social adaptation ....................................................................................... 23
Traffic accidents..................................................................................................................... 24
Crime ..................................................................................................................................... 25
5
The main conceptual elements ...........................................................................26
5.1
Antecedent factors of problem cannabis use ........................................................................ 26
5.2
Acute effects of problem cannabis use ................................................................................. 27
5.3
Chronic effects of problem cannabis use .............................................................................. 28
5.4
Secondary effects of problem cannabis use ......................................................................... 30
6
Data analysis of national reports on treated problem cannabis users
in Europe ..............................................................................................................31
Prevalence ............................................................................................................................. 32
Treatment demand ................................................................................................................ 33
Characteristics of problem cannabis users ........................................................................... 34
Treatment needs and referrals .............................................................................................. 35
7
Recommendations for research and methodological developments
for assessment at European level .......................................................................39
8
Bibliography .........................................................................................................41
8.1
Assessment ........................................................................................................................... 41
8.2
Substance .............................................................................................................................. 42
8.3
Problem use........................................................................................................................... 43
iii
TABLES
Table 1: Global scheme of different aspects of problem cannabis use as discussed
in this report ...........................................................................................................10
Table 2: Antecedent factors of problem cannabis use ..........................................................26
Table 3: Overview acute effects of problem cannabis use ....................................................27
Table 4: Overview chronic effects of problem cannabis use .................................................29
Table 5: Overview secondary effects ....................................................................................30
Table 6: Prevalence of problematic cannabis use (PCU) in Europe ......................................32
Table 7: Demand for treatment for PCU in Europe ...............................................................33
Table 8: Characteristics of PCU clients in treatment in Europe .............................................34
Table 9: Treatment needs and referral for PCU clients in Europe .........................................36
Table 10: Special treatment offers for PCU in Europe ..........................................................38
iv
1 Introduction
1.1
Background
While the early days of the cannabis discussion were dominated by very general positions in
relation to use or non-use today more specific questions are discussed. A crucial question in
this respect is, which negative consequences might arise from cannabis use (Strang, Witton
& Hall 2000).
The lifetime prevalence of cannabis use in the adult population in the member states of the
European Union is between 20 and 25%, cannabis has been used within a 12 months
period by 5 to 10% of the population. For adolescents and young adults the prevalence of
cannabis use during the last 12 months is about double as high (EMCDDA 2003). The
frequency of use as well as patterns of use vary considerably, as surveys show (e.g. Kraus &
Augustin 2001). Many people use cannabis only during a relatively short period in their
lifetime and stop this habit completely afterwards (Perkonigg et al. 1999).
Whenever an intervention is planned for this group, the heterogeneity of cannabis users has
to be taken into account. While experimental users of cannabis seldom experience negative
consequences of the substance, intensive, regular, long term or dependant use of cannabis
can much more often lead to therapeutic needs and types of treatment, which should be
tailored accordingly (Steinberg et al. 2002). The subject of this overview are problems
related to regular or intensive use of cannabis. The term “problem cannabis use” (PCU)
indicate throughout this text, that not experimental, low frequent use of cannabis is the
primary interest here, but regular, intensive use of the substance. This use might fulfil the
criteria of a “dependence syndrome” (ICD-10, DSM-IV) or “harmful use” (ICD-10) re. “abuse”
(DSM-IV). As there is no simple cut-off between “use” and “problem use” also research on
cannabis users in general has been included. In these cases problem drug use has been
defined through parameters of intensity or frequency of use.
1.2
The project
This report is the output of a project, which was conducted with the financial support of the
European Monitoring Centre on Drugs and Drug Addiction1. Parts of this report are based on
the outcome of a recent German study on clients with primary cannabis related problems in
out-patient care (“Cannabisbezogene Störungen: Umfang, Behandlungsbedarf und Behandlungsangebot [Cannabis related disorders (CareD): Prevalence, Service needs and
Treatment provision]2). This report was based on the collection of the most relevant recent
publications on cannabis, in particular international reviews. This material was
complemented with recent publications from the years 2000-2004 and chapter 15 from the
1
Project code CT.2003.103.P1
2
The project was financially supported by the German Ministry of Health and Social Security (BMGS)
1
national REITOX reports 2003 produced by the EMDDA National Focal Points in all Member
States and some of the acceding countries.
The following main topics were formulated at the beginning of this project:

regular, intensive or dependent use (=”problem use”) of cannabis

risk factors for PCU

chronic and acute problems correlated with PCU

availability and illegal market

potency of cannabis, THC contents
The outcome of this project should include
1.3

Bibliography of the most relevant publications since 1995, given the above mentioned
focus of interest

List of the instruments to assess regular/intensive use of cannabis

Framework concept of problematic use of cannabis based on the main elements from
the literature

Proposal for future developments needed in research and methodology in order to
prepare a more complete and comparable European analysis on problematic
cannabis use
Implementation
The literature search was focused on aspects of negative consequences, patterns
(frequency, duration, onset) and clinical aspects of use (diagnoses). The resulting overview
is based on the reviews published more recently by Hall & Room (1995), Kleiber & Kovar
(1998), Hall, Degenhardt, Lynskey (2001), Inserm (2001) and the Ministry of Public Health in
Belgium 2002. In addition more recent publications were searched using the internet via
scientific data bases (DIMDI, PubMed) as well as specific information providers in the field
(e.g. www.cannabisschizophrenie.com). As far as no specific search engines were available
www.goole.de was used with the keywords „cannabis“, „marihuana“ and “marijuana”.
The EMCDDA National Focal Points have as part of their national reports for the year 2003
elaborated a special topic on cannabis. Some of the literature mentioned there has also been
included here.
2
2 Assessment tools and instruments
Problematic use of cannabis can be assessed either through a specified pattern of use,
which can be observed and classified as problematic on the basis of defined cut-off points
between problematic and non problematic use as done in chapter 2.1. If a system of
classification is used instead, the decision between problematic and non problematic use are
made on the basis of weighted parameters on patterns of use, user’s behaviour, and
negative consequences or use.
2.1
Assessing problem cannabis use through patterns of use
Problematic use can be defined on the basis of frequency and patterns of use. The cut-off
between use and PCU can be defined through a frequency of use during different time
periods (lifetime, last year, last 30 days) or the number of consumption days during these
periods. Other aspects of the pattern of use (day-time, social setting, working-situation of
use) have also been taken as a proxy for PCU in some cases. The EMCDDA model
questionnaire includes a question on frequency of use during the last 30 days, which would
offer of the elements described.
2.2
Assessing problem cannabis use through clinical aspects of use
PCU can also be defined as dependent or harmful use according to existing systems of
classification. Consequences of use, tolerance development, craving and other aspect
besides the pattern of use are the basis of such a diagnoses. The key terms here are
“harmful use” and “dependence syndrome” as defined by WHO “International Classification
of Diseases”, (Dilling et al. 1999) and “abuse” and “dependence” as defined in the
“Diagnostic and Statististical Manual” (version IV) by the American Psychiatric Association
(APA 1994). While the concept of dependence is very similar in both systems, harmful use
and abuse do not correlate very well and are partly based on different definitions and
concepts. As Regier at al. (1998) pointed out, even if a diagnosis has been proved reliable
and valid, there might be a need to restrict the relevant number of cases to those, which
include a “medical necessity” of treatment. This might further reduce the number of cases.
CIDI
An interesting development in this field is the Diagnostic Interview Schedule (DIS). It has
been applied within the Epidemiological Catchment Area Study (Regier et al 1990; Regier et
al. 1998) and was further developed later into the Composite International Diagnostic
Interview (CIDI) (Robins et al. 1988; Wittchen et al. 1991). The instrument is available in a
paper-pencil as well as in an computerised version and covers the most relevant psychiatric
diagnoses including substance disorders. It can produce DSM-IV as well as ICD-10
diagnoses. The items of this instrument have been applied in the German national survey on
psychoactive substances (Kraus & Augustin 2002) where they offer DSM-IV compatible
diagnoses from paper pencil questionnaires filled in by the subjects.
3
An international WHO study on the reliability and validity of instruments measuring alcohol
and drug use disorders has included the Composite International Diagnostic Interview (CIDI),
and a special version of the Alcohol Use Disorder and Associated Disabilities Interview
schedule-alcohol/drug-revised (AUDADIS-ADR). Overall the diagnostic concordance
coefficients were very good for dependence disorders (0.7-0.9), but were somewhat lower for
the abuse and harmful use categories (Ustun et al 1997). An early study on the CIDI
(Wittchen et al. 1991) found good to excellent interrater agreements and kappa values.
CRAFFT
The Car Relax Alone Forget Family or Frinds Troubles (CRAFFT) is a short 5-item test to
screen adolescent clinical patients on alcohol related problems as well as on frequent use of
alcohol or cannabis. It offers a classification into the categories “any problem” (problem use,
abuse, dependence), “any disorder” (abuse, dependence) and “dependence” and shows
good psychometric results for general clinical populations (Knight et al. 2002) and in specific
ethnic groups. The instrument has been applied successfully with American-Indian and
Alaska-native Americans (Cummins et al. 2003).
CUDIT
Based on the items of the Alcohol Use Disorders Identification Test (AUDIT) (Saunders et al.
1993) a test has been developed for a clinical target group to screen for cannabis abuse or
dependence. The Cannabis Use Disorders Identification Test (CUDIT) was found superior to
the self-reported frequency of use in a group of out-patient clients with a mild to moderate
alcohol dependence. The Diagnostic Interview for Generic Studies (DIGS) was used as
criterion (Adamson & Sellman, 2003).
EuropASI
The EuropASI is the European adaptation of the fifth edition of the Addiction Severity Index
developed by McLellan and colleges (1985), has been translated into a number of European
languages. The complete version has been published by an group of experts (Kokkevi &
Harters 1995). A number of instruments has been developed in different countries for the
assessment of clients in clinical settings in addition to that.
Unfortunately, most of the clinical instruments are difficult to apply as part of surveys in the
general population due to their size. The application of the EuropASI requires more time than
available in most cases as well as skilled interviewers with a considerable degree of clinical
experience.
4
MECA
The computerised version of NIMH Diagnostic Interview Schedule for Children Version 2.3
was used in the Methods for the Epidemiology of Child and Adolescent Mental Disorders
Study (MECA) for surveys of children and adolescents in an unscreened population-based
sample of 7.500 households (Lahey et al 1996). Besides demographic data and information
on service needs and utilization substance use as one of several fields has been covered by
the diagnostic procedures. The instrument has been described by Shaffer et al. (1996).
SDS
The Severity of Dependence Scale (SDS) has been developed as a short, easily administered scale to measure the degree of dependence on the basis of five items (Gossop et al
1995). The drug user is requested to judge different aspects of craving and loss of control in
relation to the substance. The instruments has been developed and validated in five samples
of heroin, cocaine and amphetamine users in London and Sidney. This instrument has been
developed for a group of highly deviant drug users with frequent i.v. use of hard drugs, cutoffs have been defined for this group. The application of this instrument to primary cannabis
users has been tried only recently by Kraus and collegues (publication in preparation).
2.3
Conclusions
For basic analyses and trend information on problem cannabis use subgroups of cannabis
users should be defined on the basis of their pattern of use. This can offer a gross estimation
of the size of the problem and give some indication on trends.
A more exact and reliable picture of the situation has to include clinical aspects. Most of the
instruments described show some short-coming. CRAFFT and CUDIT have been tested only
in clinical populations, which might not be sufficient to show their validity and applicability in
the general population. EuropASI has been quite successful in clinical research but might be
too time consuming for epidemiological research in the population. When PCU is understood
in terms of harmful use and dependence CIDI items and CIDI as an computer based
instrument for data collection is a promising instrument. They have been applied in a number
of studies over the last years and shown good psychometric characteristics. Also promising
but less tested is the MECA, which might be a useful instrument especially for children and
adolescents.
Further publications on methodological aspects of the assessment of problem cannabis use
have been included in the bibliography at the end of this report.
5
3 The substance
3.1
Availability and illegal market
Availability and drug use
Availability of drugs and easy access to the substance are crucial factors for all types of
psychotropic substances (Mahhadian, Newcomb & Bentler, 1986). Korf (2002) found
parallels between the development of availability of cannabis on the Dutch illegal market and
the level of consumption in the population. Many factors play a role in this complex system of
interactions. The influence of the availability of cannabis on the development of cannabis use
is shown by Coffey et al. (2000): In a sample of male pupils in Australia drug using peers and
high availability of the drug at the age of 15 correlates with daily use of cannabis at the age
of 18.
Availability of drugs can be measured in two ways: perceived availability offers the view of
the user while the observation of the illegal market gives a more objective description of the
situation. Both ways have been used and both involve certain problems to collect the
information in a reliable and valid way.
Perceived availability
Information on perceived availability is part of some of the surveys conducted in EU member
states. The answers offer an insight in trends and allow to compare availability for different
substances. They do not give, however, an completely objective picture of the situation. Data
have been published for example for Germany (Kraus & Augustin 2001). At an European
level Eurobarometer (EORG 2002) offers this information. As there is often no indication,
how extensive the subject’s personal experiences with purchasing drugs are, the quality of
this information is difficult to judge. In some cases it might only reflect the public stereotype
on cannabis in the society. Information on drug consumption should be used to check the
quality of information on perceived availability.
Drug market
Another way to assess availability of cannabis starts from the drug market. As this is an
illegal market, official sales figures are not available and other indicators have to be used
instead. Seizures as published by the police or customs count those samples, which have
NOT reached the market. They are therefore only an indirect indicator of the amount of
cannabis offered or sold. The total amount cannot be calculated from that figure with an
acceptable degree of exactness. However, as on the whole there is little evidence, that the
effectiveness of law enforcement has changed very much during the last 10 years all over
Europe, seizures can be taken as an indicator of trends at least.
The positive correlation between perceived availability and the quantity of cannabis-related
seizures, which was found in Canada (Smart & Adlaf 1989) shows, that both sources
correspondent quite good.
6
Other ways to assess availability
Calculations on the basis of production statistics – as done for example for heroin - are not
helpful for cannabis, as a considerable percentage of the substance nowadays is produced
in-house in Europe. The techniques applied by ONOCP to estimate the heroin production on
the basis of the area of poppy cultivation cannot be used in the case of cannabis.
7
3.2
Purity
Trends in purity
Purity of cannabis raisin and marihuana has remained rather stable for a long period of time.
At the end of the 80s, Mikuriya and Aldrich (1988) pointed out, that high potency cannabis
would have been available already in the 19th century and found that raisin then had about
the same range of THC contents as reported by Perry for 1977: 5-15%. For marihuana the
range is given as 2-5%.
Studies indicate since then an increase in THC contents in Europe< (e.g. Bundeskriminalamt
2003) as well as in the United States (ElSohly et al. 2000). An considerable increase in the
THC concentration has been reported within national REITOX reports (e.g. Simon et al.
2002). Compared to Australia (Hall, Degenhardt, Lynskey 2001) the purity of marihuana is
higher here and close to hashish (BKA 2001). It has been indicated, that the average purity
for the bigger part of the cannabis on the market remained rather stable while an increasing
number of high potent samples with an THC contents above 15% or even 25% can be found
nowadays. An evaluation of French data for the years 1993 to 2000 point to this conclusion
(Mura et al. 2001).
The considerable increase in the average THC content might be caused through more potent
seeds, which have been cultivated over the last 20 years. In-house growing, which can
provide perfect growing conditions (light, humidity, water, nutrients), a highly developed
industry offering help for growing cannabis (e.g. www.buydutchseeds.com,) and special
journals ( e.g. Hanfblatt in Germany) and helplines for growers like help to optimise cannabis
production not only in professional production.
Effects of increased purity
More potent samples of cannabis might increase consumption risks. Possible negative
effects could be a faster development of dependence or other negative effects of intensive
use of cannabis.
At the moment there is little evidence for that assumption. One useful bit of information
concerns the very limited role cannabis oil has played over the last 20 years on the illegal
market despite its very high THC content. A comparison of cannabis users in treatment, who
were classified due to there pattern of use into low, medium and high risk groups, showed
significant differences in the frequency of cannabis consumption but not in the amount of
substance used per consumption (Simon & Sonntag, in press). An easy way to increase the
amount of THC per consumption would have been to use higher amounts of the substance.
As this did not happen at least in the group under observation, high potent cannabis might
not change consumption risks.
A possible positive effect of high potent cannabis is shown by Matthias et al. (1997), who
compared the tar delivery through one cannabis cigarette, using THC contents between 0
and 3,95%. They found a lower tar intake with the high potent substance for some of the
subjects, which they explain by a reduced intake of smoke.
8
Research on the pharmacokinetics of cannabinol showed in a group of six men a systemic
availability of THC from 6 to 65%. This high variability underlines, that THC contents is only
one of many factors, which influences the strength of effects (Johansson et al. 1987). Even if
users would prefer stronger effects, high potent sorts could not produce automatically strong
effects.
An analysis of drug seizures made in an region of Denmark in 1992 and 1993 also found a
great variation of purity for all drugs examined and stated, that it would be difficult for the
user to obtain the same quality of a substance each time (Kaa & Bowman, 1998).
On the whole there is no empirical evidence that the availability of high potent cannabis has
changed the pattern of use in a problematic way. It might, however, have epidemiological
effects which are not visible yet.
9
4 Problematic use of cannabis
Antecedent and consequent factors are discussed in the following chapters. The first one is
seen as a possible cause or contributing factor for the development of PCU, the latter as an
effect or consequence of the drug using behaviour. Doing this, it should be kept in mind, that
such an distinction can not always be made. Problematic situation in the family of origin or
school problems which might have been contributing factors for PCU can further develop and
become even more problematic after PCU started. As making the distinction between
antecedence and consequence helps to organise this report it has been done despite the
problems described above.
The overview on contributing factors and effects has been organised on the basis of the
distinction between short-term/acute and long-term/chronic effects and the question, if these
effects would apply to the user or the social environment around him.
Table 1:
Global scheme of different aspects of problem cannabis use as discussed
in this report
Subject
Aspects
Antecedents
Acute effects
Chronic effects
User
Use of psychotropic
substances
Mental disorder
Somatic
Mental
Somatic
Mental
4.1.3
4.1.4
4.2.2
4.2.3
4.3.2
4.3.3
Secondary effects
Social environment
Demographic factors 4.1.1
Family, social situation 4.1.2
Children
Adaptation
Traffic accidents
Crime
4.4.1
4.4.2
4.4.3
4.4.4
Attached: number of chapters in this report, where the topics are discussed
4.1
Antecedents of problem cannabis use
Research carried out in Europe, the US, Australia and New Zealand, found a number of
individual factors correlating with the occurrence of problematic consumption of cannabis.
However, we have to point out that the available list of possible risk factors has to be
regarded as preliminary (Höfler et al. 1999) and that the links are complex. Küfner et al.
(1999) have summarized various risk factors, but many of the associations found between
client characteristics or behaviour and PCU are only significant until aspects of social and
personal situation, family of origin or socio-economic status are taken into consideration as
covariates (Inserm 2001).
10
4.1.1 Demographic factors
On the whole there is a higher risk for men to develop problematic use of cannabis (Höfler et
al. 1999). This applies to most psychoactive substances. According to a Swiss survey
experience with cannabis correlates positively with the level of education, but frequency of
use (as an indicator of PCU) shows the opposite patters: the higher the level of education
the lower the frequency of use. The percentage of daily users is almost three times (12,9%)
as high among people with low education than among people with high education
(Fahrenkrug, Müller R., Müller S. 2001).
4.1.2 Family background and social situation
Family factors are highly important (Inserm 2001). Negative effects were found for drug use
of the mother (Kleiber & Soellner 1998) as well as alcohol problems of the mother (Duwe,
Schumann, Küfner 2001). In an US national household sample (N= 4.023; 12 - 17 years)
sexual assault and being a witness of violence correlates with an increased risk of substance
abuse/ dependence. A study in Norway found, that interrupted education or living with only
one or none of the parents correlates with more extensive use of cannabis (Pedersen 1998).
Especially during adolescence peers have a strong influence. This applies to the
consumption of cannabis (Inserm 2001), where peer groups seem to influence consumption
behaviour of their members and cannot been see only as gathering together on the base of
priori common interests in drugs. For the development of PCU, however, peer group effects
are significantly lower (Shedler & Block 1990, Höfler et al. 1999).
When discussing the role of the peers we have to keep in mind, that they are not chosen by
chance and that the peer group is not developing by chance, but young people join together
because they share certain characters, targets and values. To a certain extent they are thus
making their choice, what influences they will be exposed to.
In special settings, for instance in youth clubs, the rate of PCU is significantly increased
(Brandstetter & Kuntsche 2001). Corr (1999) reports 35% of current cannabis users in a
sample of homeless people, Torres & Gomes (2002) finds 38,7% of recent users amongst
prison inmates. These are selective, partly highly deviating groups who differ by a number of
characteristics from the average population. An increased risk to develop problematic
cannabis use always can be explained at least to a certain degree on the basis of these
factors.
In a sample of pupils in Australia males who had drug using peers at the age of 15 showed
an increased risk of PCU at 18. For females high-dose alcohol use and antisocial behaviour
at 15 increased the risk of PCU at 18. For both cigarette smoking is an important predictor
(Coffey et al. 2000).
11
4.1.3 Use of other psychotropic substances
The use and - even more – PCU is correlated with the consumption of legal psychotropic
substances. Drinking alcohol and smoking tobacco before the age of 14 as well as getting
drunk (for the first) time under the age of 14 is associated with the development of a
problematic cannabis use later (Duwe, Schumann, Küfner 2001). Höfler et al. (1999) point
out that also nicotine addiction has to be considered as a risk factor, while biosocial
indicators do not have any predictive value.
Usually cannabis is the first – and often the only – illegal drug used. When other drugs are
used in addition to that, the risk of addiction is increased and regular use is more frequent
(Kleiber & Soellner 1998).
4.1.4 Mental disorders and problems
Whereas experimental use of cannabis for young people correlates positively with social
conformity, PCU can be found more often among young people with personality and social
behaviour disorders (Shedler & Block 1990). Psychopathological effects can often be visible
before the beginning of drug use (Kessler et al. 2001). Behavioural or conduct disorders
during childhood, for instance committing robberies, truancy or falsifying signatures (Duwe,
Schumann, Küfner 2001), have predictive value for later drug use, especially by female
consumers. Whereas affective disorders do not appear frequently during past history, the risk
of later PCU is increased by ADHD (Höfler et al. 1999). Kessler et al. (2001) show that early
psychological disorders are valid predictions not only for drug use but above all for
problematic or addictive use. This study does not specially apply to cannabis but to drug use
in general.
4.2
Acute Effects
4.2.1 Overview
The acute effect of cannabis varies considerably within and between individuals.
Inexperienced users often do not feel any effect. Only in few cases this effect is felt to be
unpleasant (Schumann et al. 2000). Johnson (1990) points out that the experienced effect
consists of an interaction between consumed quantity, the amount of active substance in it
(=purity), the mode of consumption (smoking or eating), and individual expectations and
social situation. Besides the chemical substance (drug) the consumer’s expectations (set) as
well as the social surrounding in which consumption takes place (setting) have an impact on
the effect (Zinberg 1984).
In many cases not only intensity but also the direction of effects may vary. Thus cannabis,
which in usually relaxing and relieving fear, can also cause fear and panic attacks even for
the same person. Effects on blood pressure may also vary – dependent on the body’s
position, sitting or lying – between decrease and increase.
12
4.2.2 Somatic effects
Intoxication
Toxicity of cannabis and its most important active substance THC is low. By far the majority
of sources state that deaths in connection with an overdose of cannabis have not been
proven until today (Kleiber & Kovar 1997; van Laar et al. 2003). A Swedish study, which
found over 5 years 71 deaths related to cannabis but no other illegal drug, is rather unique
(Fugelstad et al. 1998). A clue on the frequency of severe physical acute problems caused
by cannabis is provided by the statistics of emergency cases in Amsterdam for the year
2001. On the whole 243 persons were registered as emergency cases because of cannabis.
Given the rather high prevalence of cannabis use in Amsterdam, this is a relatively low
figure.
Mortality
A Swedish study carried out among military conscripts found a higher mortality at a later date
amongst persons with increased cannabis consumption at the time of their medical
examination. However, this association was reduced considerably by taking into
consideration several mediating variables: later use of more severe drugs after, getting in
touch with police for several times, increased alcohol consumption, and early psychiatric
diagnosis. These parameters showed a correlation with increased cannabis use on one hand
and an increased mortality at a later time on the other hand (Andréasson & Allebeck 1990).
According to other studies increased mortality due to HIV/ AIDS (Hall & Solowij 1998) is
another mediating factor between cannabis use and mortality. When correcting the variables
for risk behaviour and homosexuality as a risk factor for HIV-infections, this association is
not longer significant (Sidney et al. 1997).
In total it can be stated, that there is nearly no evidence, that cannabis as a substance
increases mortality. However, there is an association between cannabis use and behaviours
which are linked to corresponding risks.
Cardiovascular effects
THC, the main psychotropic substance in cannabis, influences heart beat and blood
pressure. Frequently it causes tachycardia and blood pressure can decrease or increase depending on a sitting or standing position and tolerance – which can causes in some cases
intense dizziness (Hall & Solowij 1998; Kleiber & Kovar 1997). Adams & Martin (1969) found
brachycardia and hypertension also in animal models. Given this evidence, Hall & Room
(1995) point out, that cannabis consumption could be problematic for people suffering from a
cardiovascular disease and Hollister (1998) considers cannabis use as risky mainly for older
people of weak health. The age distribution of cannabis use shows a very small prevalence
in this age group, however.
13
Respiratory system
Wu et al. (1988) found after smoking cannabis five times as much carboxyhemoglobin in the
blood and three times as much tar in the smoke compared to tobacco. 1/3 more tar remains
in the respiratory tract because cannabis smokers breath deeper and inhale longer.
Psychomotor effects
Cannabis reduces performance of short-term memory, concentration, attention, and
psychomotor coordination. Hall & Solowij (1998) report about effects in laboratory
experiments corresponding to an alcohol intoxication of about 0,7-1,0 pro mille. The extent of
this effect may, however, vary considerably. For more details please see chapter 4.4.
Other somatic effects
Consumption of cannabis may cause sickness and vomiting in some cases (Berke & Hernton
1974), but an increased appetite is a typical short-term effect of cannabis intoxication. More
frequent dryness of eyes and mouth, cough and impaired balance are found (Kleiber &
Soellner 1998). All these effects are in general light to moderate.
4.2.3 Mental effects
The most frequent acute psychological effects of cannabis use are euphoria and feeling well
at first, which are followed by sedative effects depending on the dosage. Changes in
perception (colours, time, space) as well as even hallucinations may appear (Hollister 1986)
and in addition the following impairments of mental functioning have been found as negative
effects..
Cognition
The effects of cannabis, which have been described as similar to an alcohol level of 0,7-1,0
pro mille, reduce cognitive performance in general. Especially the ability to concentrate and
attention span as well and short-term memory are reduced, which has negative impact on
performance in school and working place (Kleiber & Kovar 1997, Tennent & Groesbeck
1972, Hall & Room 1995, Hall & Solowij 1998)
Dysphoria, anxiety and panic disorders
The anxiety relieving and sedative effects of cannabis can also turn into the opposite. Selfreports of cannabis users in New Zealand showed that 14% of the men and 30% of the
women experienced panic attacks after using cannabis (Thomas 1996). Negative effects on
mood (dysphoria) (Berke & Hernton; Hall & Solowij 1998; Hall & Room 1995) and anxiety as
well as panic attacks were reported by a number of sources (Berke & Hernton 1974; Hall &
Solowij 1998). It seems that experienced consumers are able to deal better with these
negative effects (Berke & Hernton 1974; Hall & Room 1995), however the risk remains about
the same that they might occur after cannabis use. Women are more frequently affected by
these negative effects (Thomas 1996).
14
Toxic psychoses
Sudden relapses into a state resembling an acute cannabis intoxication without having used
cannabis („Flashbacks“) have been reported in individual cases but there is neither a clear
description nor reliable figures about the frequency of this phenomenon. On the whole it
seems that such effects are more frequent when using hallucinogens and temporal in any
case (Tennent & Groesbeck 1972). Consumers of cannabis may have psychotic states in the
course of intoxication, especially under very high dosages (Tennent & Groesbeck 1972). A
research study amongst recruits in the German Army found, that the number of persons
discharged from military service because of psychotic disorders doubled between 1988 and
1992 (Wimmer & Mahlberg 1996). Similar developments were found among American
soldiers in Germany earlier, where an increase in the number of schizophrenic reactions
followed a significant increase of drug use in this population. However, in these cases the
persons consumed many different drugs and effects cannot be seen in connection with
cannabis use only (Tennent & Groesbeck 1972).
The concept “cannabis psychosis” is not used today any longer by many experts as they
argue, that this pattern of symptoms can be described adequately through “toxic psychosis”
without defining an additional diagnosis. This state is caused in most cases by consumption
of medium up to high doses of cannabis (Thornicroft 1990).
4.3
Chronic Effects
4.3.1 Overview
It is difficult to record long-term effects of cannabis use. A number of animal experiments
showed such effects but can serve only as a model and inform about possible risks (Adams
& Martin 1996). In many cases there is a lack of human studies, in other cases the effect of
cannabis use can hardly be separated from effect though tobacco or other drugs. As
cannabis is often used mixed with tobacco, the negative effects of tobacco smoking are also
always involved.
In the following chapter effects are described which are very likely caused by cannabis use
due to present knowledge. For a general survey of research results especially see Kleiber &
Kovar (1997) and Inserm (2001). Although cannabis users exhibit some negative deviations
and additional health risks in comparison to the remaining population, they make hardly more
demands to the healthcare system (Hollister 1998). Even long-term cannabis users do not
report more health problems than a control group (Coggan et al. 2002).
4.3.2 Somatic effects
Respiratory system
One of the most important risks concern damages to the lungs and respiratory tracts (Hall &
Room 1995). Acute effects in this are hoarseness etc. The effects of cannabis on breathing
constitute acute risks for asthmatics (Hall & Room 1995). A chronic damage to the bronchial
tubes is associated to the use of cannabis as well as a reduced function of the lungs (Hall &
15
Solowij 1998, Inserm 2001). In animal experiments carcinogenic effects of cannabis smoke
were proved, but the clinical relevance of these results could not yet be shown in human
studies(Hall & Solowij 1998).
Comparing the composition of tobacco smoke and cannabis smoke, similar effects especially
in relation to the development of lung and gullet cancer can be expected. There seem to be a
higher risk compared to tobacco only as cannabis is burning under higher temperatures and
is inhaled more deep that tobacco (Hall & Solowij 1998).
Wu et al. (1988) found after smoking cannabis five times as much carboxyhemoglobin in the
blood and three times as much tar in the smoke compared to tobacco. 1/3 more tar remains
in the respiratory tract because cannabis smokers breath deeper and inhale longer.
However, the number of joints smoked per day is considerably below the number of tobacco
cigarettes smoked for most people, which again reduces the total effect of cannabis. THC as
active substance in cannabis has practically no influence on these negative effects, which
are rather exclusively caused by burning the additional substances included in cannabis or
marihuana.
Reproduction
Negative effects on the reproduction system have been proved up till now only in animal
experiments (Hall & Room 1995). Early results concerning restriction of the number of
sperms of men have not been confirmed.
Other somatic effects
Suppressed functioning of the immune system through THC were proved in animal
experiments, but there are no valid results from human studies (Hall & Room 1995).
Neurological damages caused by cannabis were found in an early study (Campbell 1971),
but also were never replicated.
4.3.3 Mental effects
In a German study (Kleiber & Soellner 1998) more than 20% of the cannabis users reported
repeated psychological problems linked to cannabis consumption. Hollister (1998) and Hall &
Solowij (1997) describe different aspects of mental health and risks connected with cannabis.
Apart from possible effects of cannabis on mental basic abilities, especially addiction and
harmful use/ abuse are relevant here. Tolerance development here and psychological
consequences for systematic reasons are discussed in this place.
Correlations between global mental health status and cannabis use have been found by
McGee at al. (2002). In a longitudinal study in New Zealand (Dunedin Multidisciplinary Health
and Development Study) mental disorders at the age of 15 were followed by a small, but
significant increase in cannabis use at 18; cannabis use at 18 was positively correlated to
mental health problems at the age of 21.
16
Poikolainen et al. (2001) and Smit, Bolier and Cuijpers (2003) draw from their research the
conclusion, that it would be more likely, that cannabis use causes mental health problems
than being a consequence of such problems.
An increased rate of coexisting psychiatric disorders was found for current users of all illegal
substances compared to non-users also in the “Methods for the Epidemiology of Child and
Adolescent Mental Disorders (MECA)” study. Especially the mood disorders and disruptive
behaviour disorders were much more frequent in this group. Cannabis plays a major role in
this group, but its effects have not been analysed separately (Kandel et al. 1999).
Based on a national mental health survey on children, a number of 2.624 subjects between
13 and 15 years were included in a study on the relation between psychotropic substance
use and global psychiatric morbidity. The strongest correlation was found for regular tobacco
smoking, a smaller effect for regular cannabis use (Boys et al. 2003).
In the Epidemiologic Catchment Area (ECA) Study, which was conducted in an US
population (N=20,291) 50,1% of all persons with a lifetime prevalence of cannabis abuse
show mental disorders (substance abused not included) during their lifetime (Regier et al.,
1990). Narrow, Robins and Regier (2002) request to look for the clinical significance of
diagnoses of mental disorders which are produced following the standards at hand. When
using demands for professional help or medication as an indication that a disorder really
interferes with the drug user’s daily life, the prevalence or mental health disorders amongst
the above mentioned problem cannabis users in the Epidemiological Catchment Area (ECA)
study is reduced to 17%, in the National Comorbidity Survey (NCS) to 32%.
Cognition
Acute negative effects of cannabis on the performance of short-term memory, concentration
and other aspects cognitive performance are well documented (Tennent & Groesbeck 1972,
Hall & Room 1995, Hall & Solowij 1998). The question is still under discussion, if these
effects are permanent. In animal experiments performance was reduced after cannabis use
for up to 3 weeks and changes of the EEG were found during long-term use (Adams & Martin
1996). On the other side a number of studies presume that up till now there is no sufficient
evidence that cannabis use causes a permanent reduction of cognitive performances. Subtle
reductions may occur which could be measured only with more suitable instruments
(Hollister 1998). Research on this topic is difficult as there is a correlation between intensity
of consumption and acute effect on cognitive performances as well as after-effects of
cannabis use which can last for more than 24 hours.
Results from an American survey among students in 140 colleges show a relationship
between (bad) marks and cannabis use. However, these users were beside there drug use
also more interested in “binge drinking”, smoking tobacco and changing sexual partners,
which might also indicate differences in their motivation of performance. Also for this reason
it has not been proven that cannabis is the reason for the defects (Bell, Wechsler, Johnston
1997).
17
Sabroe and Fonager (2002) found a negative association between cannabis use and school
performance in Denmark, which might be caused by reduced ability to concentrate as it has
been found in another study (van der Poel et al 1999).
The negative effect might depend on the dosage. Tennent & Groesbeck (1972) found in a
study carried out among American soldiers in Germany that consuming up to 12 grams of
cannabis per month caused hardly any negative effects while consumption of alcohol
correlated with disorders in the fields of concentration, memory and judgement.
The same conclusion can be drawn from the study of Pencer and Addington (2003), who
found no significant correlation between cognitive disorders and light up to mediocre
cannabis use for mentally ill persons.
Comparing IQs, which were assessed at the age of 9 to 12 years and again 8 years later, a
decrease of (on the average) 4.1 points was found for persons, who were smoking cannabis
at least five times per week at the time of the second assessment. All other groups including
light users and former users of cannabis show an increase in IQ points over the same time
period. The authors draw the conclusion, that cannabis had no long term negative effect on
global intelligence but negative short term effects (Fried, Watkinson & Gray, 2002).
A meta-analysis by Grant et al. (2003) show, that differences in cognitive functioning
between users and nonusers a no longer significant after users have gone though an
abstinence period of a minimum of 3 weeks.
Development
Cannabis use is especially popular among young people (von Sydow et al. 2001). This stage
of life is of special importance for personal development. It is marked by trial and error and
testing the own limits. Drug use – particularly the consumption of cannabis – is one aspect of
this risk behaviour. Shedler and Block (1990) show, that experimenting with cannabis is
rather a sign of mental health at that age. However, this does not apply to regular and
frequent use, which can cause or intensify problems.
Cannabis use is associated with a higher rate of school dropout (Hall & Solowij 1998) as well
as the consumer’s entry into the drug scene (Lynsksy 2003). A number of confounding
variables play a role here and Hall & Solowij (1997) do not confirm an negative effect of
cannabis use on psychosocial development as such. Cannabis use is not very much the
reason for a number of problems but works as an amplifier of such problems. Forming
groups with other cannabis users may intensify the already existing non-conformism. Already
existing conduct and behavioural problems in early childhood and early use of legal substances etc. may worsen the problem situation by choosing a corresponding peer-group and
obstruct the development of personality (Hall & Room 1995; Brandstetter & Kuntsche 2001).
18
Depression and suicide
As a consequence of cannabis use also depressive disorders may occur. Inserm (2001)
point out that there is an increased risk for suicide among consumers of cannabis. However,
the substance may not be the only cause, but again is interconnected with a number of
succeeding behaviours (use of hard drugs, intravenous drug use) which are increasing the
risk of suicide. Patton and colleagues (2002) found in a longitudinal survey carried out for a
period of 7 years among an Australian cohort of pupils in secondary schools (N=1601), that
using cannabis at least once a week for girls doubled the risk of developing depression or
anxieties after 6 years. Daily use of cannabis is linked to a fivefold higher probability. The
opposite sequence – cannabis use following depression or anxiety disorders - showed no
significant effect, which support a causal role of cannabis use (Patton et al. 2002).
In a longitudinal survey, Bovasso (2001) also found a correlation between cannabis use and
depression. For persons without depressive symptoms the risk to show symptoms of
depression after 15 years were about four times as high when they were cannabis users
compared to non-users. Factors like age, sex, antisocial personality and others have been
used as covariates.
Jääskeläinen (2003) and Poikolainen (2002) conclude from their studies, that cannabis use
make persons more liable for depression. Fergusson and Horwood(1987) indicate that
Persons with cannabis abuse or addiction are also more affected by other psychiatric
disorders in general.
Schizophrenia
One of the main points of discussion in relation to cannabis risks are psychotic and
schizophrenic disorders. An epidemiological longitudinal study among army conscripts in
Sweden found an increased risk of schizophrenic disorders for cannabis users 15 years after
the time of medical examination (Andréasson et al. 1987, Allebeck, Adamsson, Engström
1993). The relative risk is 6.0% for persons having used cannabis more than fifty times.
There was no former diagnosis of psychological disorders before starting cannabis use, but it
cannot be excluded that the substance is used as self-medication for a beginning
schizophrenia. An up-to-date analysis using data on schizophrenic diseases in the Swedish
register up to the year 1996 found a relative risk of 6.7%. When cases of schizophrenic
disorders appearing within 5 years after medical examination are excluded to guarantee the
chronological sequence between cannabis use and psychological disorder, the results were
similar (Zammit et al. 2002). While schizophrenic disorders are as frequent in families of
cannabis users and of non-users, negative social conditions are more frequent in users’
families. Johnson, Smith, Taylor (1988) object, that many of the subjects in this study used
amphetamines in addition to cannabis. The known psychotic effects of this substance might
be diagnosed erroneously as schizophrenia.
A recent longitudinal study (Arsenault et al. 2002) could show by means of a relatively small
population that cannabis use in the age of 15 respectively 18 years increases the probability
19
of schizophrenic disorders at the age of 26 even if pre-existing psychosis was controlled for.
An earlier use showed more significant effects.
In a Canadian study a random survey among an adult population out of 2144 households
found a lifetime prevalence of 8.0% abuse or addiction of drugs and of 0.7% for
schizophrenia. The lifetime prevalence of drug abuse and addiction was 50.8% among this
group and thus about 6 times as high as among the entire population. Although this study
does not report explicitly effects of cannabis, the high availability of cannabis as well as the
high affinity of schizophrenic people for this substance give rise to the suspicion that
extensively cannabis was concerned (Bland, Newman & Orn 1986).
In a high-risk-group of persons with subliminal psychotic symptoms or a high burden of
relatives with such disorders, cannabis consumption or cannabis addiction does not increase
the risk for developing psychosis during a period of 24 months (Phillips et al. 2002).
Dixon and collegues (1990) point out that cannabis effects might be interesting for persons
people with schizophrenic disorders to calm down disagreeable sensations. Because of the
anti-depressive and sedative effects cannabis might be preferred to alcohol, cocaine or
opiates (Schneider & Siris 1987). The “socialising effect” which helps to reduce the distance
to social environment is also considered as positive (Dixon et al. 1990).
When analysing the clinical populations of schizophrenic patients, users of cannabis show an
earlier outbreak, but no differences in family anamnesis, pre-morbid social development,
outcome (Eikmeiner et al. 1991) or neuro-cognitive effects (Cleghorn 1991). Other studies
found only small differences between cannabis users and non-users in a clinical population
(Dixon et al. 1990).
A crucial question is, whether cannabis causes schizophrenic phases or if can only trigger
them on the basis of an existing vulnerability. Hall & Room (1995) assume that the latter is
the case and that cannabis use worsens the course of development after the outbreak. If
cannabis causes schizophrenia or increases positive symptoms, the total effect must be
relatively small as the strong increase of cannabis use in the population in Western societies
during the last decades has not produced a visible increase in the prevalence of psychosis in
the population (Hall & Solowij 1997). Only some examples are known: an increase of
psychotic disorders – however not specifically for individual drugs – took place parallel to a
significantly increase of drug use in the US army in Germany (Tennent & Groesbeck 1972);
Kay (1992) points out that people from the Dominican Republic resident in Great Britain as
well as in their home country show rates of schizophrenic disorders (11.8/1000) which are 6
to 8 fold to the British population. In the African countries of origin of their genotype there is
no increased rate of schizophrenic disorders to be found. The authors conclude, that the
intense use of cannabis in this population may be a reason for the increased rate of
schizophrenic disorders. Similar experiences have also been reported from the former
French colonies.
The substance can increase to a certain extent the symptoms of psychosis (Hall & Solowij
1998). Long-term use is correlated with worse conformity and more addiction problems in the
family (Caspari 1998). Relapses into psychotic states happen more frequent and earlier
20
among cannabis users (Linszen, Dingemans & Lenior 1994). Häfner and collegues (Häfner
et al. 2002) examined the chronological sequences of consumption and schizophrenic
symptoms of a group of persons with first schizophrenic periods of illness and found
indications that cannabis should rather to be regarded as unsuitable attempt of selfmedication than as a trigger.
Pirkola (2003) draw the conclusion, that cannabis increases the risk of schizophrenia for its
users, but still feel that genetic factors have a bigger influence in this development.
In a Dutch survey cannabis use is correlated with an increased number of psychiatric
symptoms and the respective need for treatment three years. These results show, that
cannabis can cause psychotic effects as well as worsen exiting ones, if a vulnerability is
given (van Os et al. 2002).
A meta-analysis published recently (Arseneault et al. 2004) comes to the conclusions on the
basis of five methodological sound studies, that cannabis use can be seen as a risk factor for
the development of psychotic disorders especially for vulnerable youths. At individual and
social level, the authors concluded, incidence of schizophrenia could be reduced by avoiding
the cannabis use.
Taking together all these results, the conclusions made by Hall und Degenhardt (2000) are
very reasonable: the link between cannabis and schizophrenia is not yet clear, but there is a
growing bulk of research indicating that cannabis worsens symptoms of an existing
schizophrenia and that it can trigger psychotic disorders when a certain vulneratbility is there.
Tolerance syndrome, harmful use and addiction
The development of tolerance towards THC is evident for intense, longer-term use of
cannabis as animal models and human research studies show (Adams & Martin 1996). The
degree of addiction seems to be not very strong as in animal experiments cannabis has only
little power as a reinforcer and significantly less medical help is necessary for withdrawal
from cannabis than for instance from heroin.
A representative epidemiological study in Germany found a lifetime prevalence (DSM-IV) of
5.5% for cannabis abuse (Lieb et al. 2000, von Sydow et al. 2001) in the age-group 14-24.
This group showed a stable pattern of use during an observation period of 4 years. A
longitudinal study in New Zealand showed 7.3% for the age group between 16 and 18 years
(Fergusson & Horwood 1997).
Cannabis dependence as a concept contains several critical aspects: preoccupation with the
substance, compulsive use and relapse or recurrent use (Miller & Gold 1989). Continuous
use despite significant negative consequences can give a first indication of dependence as
defomed above (Reynaud & Schwan, 2003).
There are in fact cases of cannabis addiction (Hall & Solowij 1997) and Hall & Room (1995)
consider this disorder even as one of the most frequent addictions in Western societies.
According to estimations in the United States 10% of intensive cannabis users become
addicted in the course of their life. The same figures for alcohol (15%), nicotine (32%) and
21
opiates (23%) indicate, that there is a comparatively low risk of becoming dependent on
cannabis (Hall & Solowij 1998). In Germany in the age group 14 to 24 a lifetime-prevalence
of cannabis addiction of 2.2% was found (von Sydow et al. 2001). In the US a rate of 2.6%
was found for the age group 12 to 17, 3.5% for the group 18 to 25 (Dennis et al. 2002). In
New Zealand 4.3% of the age group between 16 and 18 fulfil the criteria of addiction in the
age between 16 and 18 (Fergusson & Horwood 1997).
Withdrawal symptoms as well as the wish to reduce respectively control consumption are the
most frequent DSM-VI criteria found for these cases (Kleiber & Soellner 1998). There is a
positive correlation of addiction with intensity of use, but not with duration of use (Kleiber &
Soellner 1998). The drug user’s subjective feeling of being addicted to the substance
correlates with DSM-IV diagnoses but is more critical than that.
In an American sample a critical value of 3 out of 7 criteria for addiction (similar to ICD-10)
was exceeded by 28% of current cannabis users. Among them persons at the age of 12 to
17 years are more often affected (43%) than persons above 25 (18%) (Dennis et al. 2002).
In an experimental setting, withdrawal symptoms during a 45 days abstinence phase were
studied amongst 18 subjects. All of them were regular cannabis users (on the average for
12.8 years) and used cannabis nearly daily before the study started. Withdrawal symptoms
found are aggression, anger, anxiety, decreased appetite, irritability, sleep problems and
others. They start 1-3 days after the start of abstinence, peak between day 2 and 6, most
effects last 4-14 days. Over 75% of the subjects experience at least four symptoms.
Magnitude and time course of effects are similar to tobacco (Budney et al. 2003).
Use of other psychotropic substances
The „stepping-stone“ theory, that cannabis use will be followed automatically by other more
risky drugs, is not supported by facts and not taken as valid also in the drug discussion.
Nevertheless the cannabis use is linked to an increased risk of using other psychotropic
substances as well.
A study amongst 311 monozygotic and dizygotic same-sex twins in Australia examines the
correlation between use of psychotropic substances before the age of 17 years and later
drug use and dependence. Early use of cannabis is associated with a higher risk of
developing alcohol dependence or drug abuse/dependence (odds: 2.1 to 5.2) compared to
non-using co-twins. Controlling for known risk factors these results remain stable. The
authors conclude, that effects of early cannabis use on later drug use and alcohol
dependence go beyond genetic or shared environmental factors.
22
4.4
Secondary Effects
4.4.1 Effects to unborn children
Children of mothers consuming cannabis show a slightly reduced birth-weight (Hall & Room
1995). Hollister (1998) is quoting Zuckerman et al. (1989) who also found that children of
mothers smoking marihuana were born smaller and lighter and had smaller heads.
Children of cannabis using mothers might show some cognitive impairment. Hall & Solowij
(1998) mention temporary restrictions in early childhood. In the Ottawa Prenatal Prospective
Study (Fried 1993) offspring of cannabis using mothers showed no effects at the age of one
year as well as at the age of five to six years, when the effect of confounding variables is
excluded. Measurement at the age of four years showed reduced performance in memory
and verbalization but it has to be mentioned that the relationship between cannabis use of
the mother and child characteristics can be mediated by other factors. For instance a
reduced parental engagement of the mother (Fischer et al. 2001), but also the use of other
psychotropic substances may play a part as confounding variable.
Performance and social adaptation
Concentration, short-term memory, speed of reaction and power of judgement are
considerably reduced during cannabis intoxication (Kleiber & Kovar 1997). There is a
significant association between cannabis use and problems of social adaptation, problems in
school and at the workplace (Fergusson & Horwood 1997), school performance (Inserm
2001; Kandel & Davies 1996), work performance (Kandel & Davies 1996; Thomas 1996) and
general social problems (Thomas 1996). Cannabis users have more family problems (Kandel
& Davies 1996). In addition to problems of concentration and general cognitive impairment
cannabis can have an negative impact on school education through increased risk of leaving
school without qualification or failure to enter university or to obtain a degree (Fergusson,
Horwood & Beautrais 2003).
Presumably many activities in school or profession cannot be carried out adequately in the
state of intoxication. There is a high probability that the speed of work as well as the quality
of its results is decreased by the reduced performance of the drug user. Studies carried out
in Greece (Stefanis 1977) and Jamaica (Rubin 1975) nearly 30 years ago found no problems
for chronic cannabis consumers to live inconspicuously and integrated into the working
society. It can be argued, that working conditions today might produce more problems for
drug users in everyday life. In this respect a loss of productivity is assumed, but has not been
confirmed by corresponding studies or estimations (Hall & Room 1995).
In the study of Shedler & Block (1990) intensive use of cannabis is correlated with a clear
deterioration of interpersonal relationship and perceived stress. The link between cannabis
use and social consequences weakens when other factors are included in the analysis
(Kleiber & Soellner 1998). As Hall & Solowij (1997) point out, early contact with Cannabis
increase the risk of using heroin or cocaine later, which should not support the “steppingstone”-hypothesis (Hall & Solowij 1998), but make clear, that these are only correlations.
23
On the whole there seem to be a correlation between the amount problems in everyday life
and cannabis use (The National Board of Health and the Danish Cancer Society 2003).
4.4.2 Traffic accidents
A cannabis level of 7 – 15 ng/ml blood corresponding to 1 joint of 10 – 15 mg THC causes
critical effects on the driving performance one hour after consumption (Schulz et al. 1998).
The typical effect of one cannabis cigarette has been is compared to an alcohol level of 0.51.0 pro mille (Hall & Room 1995). The acute effects disappear after 24 hours at the latest
(Kleiber & Kovar 1997) but signs of reduced cognitive functioning have been found up to 3
weeks after cannabis use.
Effects on the fitness for flying of pilots could be testified up to 24 hours (Hollister 1998). An
estimation of the effects is difficult as the substance, the mode of consumption and individual
reactions may vary considerably (Schulz et al. 1998). Moreover, consumers of cannabis
sometimes overestimate their state of being “high” and compensate a part of the restrictions
by driving more slowly and carefully. In contrast to persons driving under the influence of
alcohol the style of driving does not become more aggressive but more defensive (Adams &
Martin 1996). Under experimental conditions clear negative effects on driving have been
found (Lagier et al. 1996, Mura 1999). In everyday life the risk of accident for this group is
only slightly increased (Ramakers et al. in press), what might be due to a more cautious way
of driving while intoxicated (Sexton et al. 2000). The risks increase considerably if cannabis
and alcohol use are combined (Inserm 2001, Vollrath et al. 2001).
When comparing different substances in statistical data about accidents and persons
causing accidents show that the risks by car drivers being intoxicated with cannabis are
comparatively lower than by persons intoxicated with other psychotropic substances
including alcohol (Inserm 2001). In a “roadside survey” investigating a representative sample
of car drivers who have been tested on the spot for different substances, cannabis could be
proved for 0,57% of the tested drivers and alcohol for 5.48%. The respective values for
opiates were 0.15-0.62% (heroin, codeine). Only one out of 2017 samples showed cannabis
in an amount (>40 ng/ml), indicating an acute reduction of performance (Krüger, Schulz &
Magerl 1998).
The association between the risk of traffic accidents and cannabis using behavior has been
examined in a longitudinal study over a period of three years. There was an association
found between cannabis use and ‘active’ traffic accidents, where the person contributed to
the accident. This link, however, seems to be mainly a consequence of differences in risk
behavior and personal characteristics (e.g. gender) between cannabis users and non-users.
(Fergusson & Horwood, 2001)
24
4.4.3 Crime
Violent crime under the influence of cannabis is rare. The sedative effect which follows soon
after consumption is rather opposing aggressive behaviours than intensifying or producing
them. Thus – in contrast to cocaine, crack or alcohol - cannabis does usually not increase
violent offences in different situations (Berke & Hernton 1974).
Cannabis use is one of several problem behaviours, which are found frequently amongst
adolescents. Jessor and Jessor (1977) have developed the concept of a “syndrome” of
problematic behaviour, where a cause-effect relationship is difficult to find. Farrell et al.
(1992) shows for 7th and 9th grade school children a high correlation between different types
of behaviour, which are perceived as problematic by their environment: smoking cigarettes,
drinking alcohol and marijuana, delinquency, early sexual intercourse. These results were
found at American urban schools, where the majority of children came from low-income
African American families. Generalisation of results to other settings might not be adequate.
25
5 The main conceptual elements
A number of studies has found empirical evidence for risks of problem cannabis use (PCU)
and negative consequences of it. The following tables give an overview on the most
important aspects of PCU. They are based on the results reported in chapter four, the
literature can be found in the annex of this report. The selection of factors described here is
based on the research outcome available. You could think of many more variables as risk
factors for the development of PCU or as negative consequences of cannabis use. The
selection shown here follows empirical evidence available when this report has been prepared. As research will continue, new risk factors and negative consequences might become
visible in future and the risks linked to cannabis may be perceived in a different way. The
overview given here should be seen as a snap-shot of the evidence available today.
5.1
Antecedent factors of problem cannabis use
Antecedent factors of problem cannabis use have been found in the field of demography.
Being male or reaching only a low level of school education is associated with an increased
risk of PCU. Early and intensive use of legal psychotropic substances, childhood mental
disorders and conduct disorders also mean increased risks of PCU. Some studies show
increased risks when the family of origin is a one-parent-family, the mother has experienced
problems with psychotropic substance or sexual assault or a dysfunction family situation is
indicated by violence inside the family. Peers can be a risk especially when drugs are used
regularly within this group or when they supply its members with the substances. In special
settings like prisons or clubs the prevalence of PCU is much higher than in the normal
population (Table 2).
Table 2: Antecedent factors of problem cannabis use
Area
Specific aspect
Demographic factors
Gender
Education
Alcohol
Psychotropic substances
Mental disorders
Family situation
Social situation
Nicotine addiction
Conduct disorders
Early psychological disorders
Incomplete family situation
Drug use mother
Alcohol problems mother
Sexual assault
Experience of violence
Interrupted education
Drug using peers
Drug supply through friends
Special settings
(clubs, prisons)
Evidence for
negative effects
+ male
+ low level
+ regular use before the age of 14
+ getting drunk for the first time
before the age of 14
+
+
+
+
+
+
+
+
+
+
+
+
Conclusions from literature on factors/effects of the specific aspect: +: evidence found
-: no evidence found
26
5.2
Acute effects of problem cannabis use
Cannabis use produce a state of intoxication which changes perception and other parameter
of somatic and mental state. It shows acute effects on heart rate and blood pressure, which
may be problematic if a preceding damage exists. Cannabis smoke seem to be much more
toxic and carcerogenic than tobacco smoke. Other acute consequences of cannabis use are
only minor obstacles for well-being and health: dryness of the mouths, dizziness.
Acute effects on memory and cognitive functioning in general have been shown. This
reduces psycho-motor abilities and interferes with the ability to drive a car or to operate
complicated machines while intoxicated.
Panic attacks, anxiety and depressive moods can appear after cannabis use. Especially
experiences of anxiety have been reported by a considerable percentage of users. More
intense negative experiences are associated to acute toxic psychoses which are connected
with a high dose and/or frequent use in most cases (Table 3).
Table 3: Overview acute effects of problem cannabis use
Area
Specific aspect
Somatic
Intoxication
Mortality
Cardio-vascular effects
pulse beat increased
blood pressure increased/
decreased
Respiratory system
Psycho-motor functioning
Others: dryness of mouth, cough
Cognition
Short term memory
Attention
Toxic effects
Toxic psychosis (“ cannabis
psychosis”)
“Flashback”
Affect
Dysphoria
Anxiety
Panic attacks
Mental
Evidence for
negative effects
+
+
+
+
+
+
+
+
+
+
+
+
Conclusions from literature on factors/effects of the specific aspect: +: evidence found
-: no evidence found
27
5.3
Chronic effects of problem cannabis use
There is an unsolved debate on the question, if effects caused through cannabis are stable
and become chronic or if all of these impairments are temporary only. In many fields risks
which have been discussed and suspected earlier or have been found in animal models have
not been verified by human research or additional studies later.
In the field of somatic effects negative consequences of cannabis use on genetics, the
immune system and reproduction have been discussed before, but these hypothesis have
not been supported by research evidence so long. Also the risk of cancer of prostate and
head or neck seems is increased through cannabis use. Critical are the effects of smoking
cannabis for the respiratory tract. The risk of bronchitis is increased and there is also
research indicating an increased risk of lung cancer through cannabis. The findings, that
cannabis smoke is much more toxic than cigarette smoke are in line with this assessment.
Until now this risk has not produced a measurable increase in caseload of lung cancer in the
population parallel to the increased cannabis use in many countries during the last 30 years.
This might be a result of a comparatively low frequency of use of cannabis for most of the
users compared to tobacco. However, it can not be excluded that these consequences will
become apparent in the population only with a delay of decades.
Chronic psychological effects have been found for cognition and memory. They last longer
than the acute effect of cannabis do prevail but there is no study which shows persisting
cognitive effects after an abstinence period of three weeks. Cannabis use can delay
developmental processes and interfere with the personal development of an adolescent or
young adult.
Cannabis use can cause harmful use and addiction as well as other problems linked to these
syndromes: tolerance and withdrawal symptoms. High frequent, intensive use of cannabis
means an increased risk of addiction; the duration of drug use does not play a crucial role in
this respect. The degree of addiction seems to be lower than for a number of other drugs
which makes detoxification easier and more successful.
A number of psychiatric problems have been discussed related to cannabis use. There is
evidence that psychotic disorders and cannabis use correlate, but it is difficult to judge the
type of association. A causal relationship is very hard to proof and – at the epidemiological
level of evidence – an increase in incidence of schizophrenic disorders has not been found
as a consequence of the increased cannabis use in the population of many countries of the
Western world. The use of cannabis as self-medication by schizophrenics tends to worsen
the situation of the patient, active symptoms of psychotic disorders are increased. Anxiety
disorders are rather frequent amongst cannabis users and increased risks of depression as a
consequence of cannabis use has been shown especially for female users. “Amotivational
syndrome” from cannabis use today is by most researchers seen as the effect on continous
intoxication through cannabis. “Cannabis psychosis” are explained by short term effects of
toxic psychosis, which can follow especially heavy use of cannabis. Long term psychotic
effects caused by cannabis are subsumed under the general syndromes (Table 4).
28
Table 4: Overview chronic effects of problem cannabis use
Area
Specific field
Somatic
Genetic harm
Immune system
Reproduction
Bronchitis
Evidence for
negative effects
+
Cancer
Lung
Bronchi
Oesophagus
Head/neck
Prostate
Mental
+
+
+
-
Perception
Cognition
Memory
Development
+ up to 3 weeks after use
+
+
Dependence syndrome
Tolerance
Withdrawal
Harmful use of other substances
+
+
+
+
Psychotic disorders
Anxiety Disorders
„Cannabis psychosis“
„Amotivational syndrome“
+
+
= toxic psychosis
= continued intoxication
Conclusions from literature on factors/effects of the specific aspect: +: evidence found
-: no evidence found
29
5.4
Secondary effects of problem cannabis use
Beside the effects of cannabis on somatic or mental health secondary effects have been
shown in several fields. Given the critical age of many of the cannabis users, which are at the
beginning of their adulthood trying to find a job and their place in life and society these
secondary effects might in many instances be the most problematic ones.
There is clear evidence, that not only motivation but also ability to perform at the level of
one´s possibilities is reduced through cannabis use. Reduced performance at school and
workplace, lower marks at school and broken-off school or university education are
associated with cannabis use. These effects are also a consequence of the cognitive
impairments caused by cannabis described above. Even if these impairments do not persist
after 3 weeks of abstinence, continuous intoxication through regular use of cannabis has the
same negative effect on the performance.
The same impairments also lead to problems in driving a car, but most evidence shows only
very limited negative effects in this respect. Cannabis users seem to counterbalance their
impairment by driving more slow and more cautiously (Table 5).
Table 5: Overview secondary effects
Area
Specific field
Unborn children
Reduced birth weight
Cognitive impairment
Social adaptation
Problem in school and workplace
Reduced school and work performance
Traffic accidents
Performance and
social adaptation
Traffic accidents
Crime
Maladaptation
Violent acts
Evidence for
negative effects
+
+ (only at the age of 4)
+
+
+
+ (small effect)
+
-
Conclusions from literature on factors/effects of the specific aspect: +: evidence found
-: no evidence found
30
6 Data analysis of national reports on treated problem cannabis
users in Europe
The results from the national reports of the following member states were used as a basis for
the following chapter. While the outline of this national chapter was defined by the EMCDDA
guidelines some of the details differ between the national reports. For that reason data are
not always completely comparable, but they can give an indication of the situation in different
member states of the EU.
The analysis is based on the respective sub-chapters of the National REITOX reports for the
year 2002 prepared by

Austria

Belgium

Czech Republic

Denmark

Finland

France

Germany

Greece

Ireland

Italy

Lithuania

Luxembourg

Netherlands

Netherlands

Norway

Portugal

Slovenia

Spain

Sweden

United Kingdom
In order to avoid duplication only the most interesting and relevant information has been
drawn from the national reports and structured around the topics of prevalence, treatment
demand, characteristics of clients, treatment needs and referrals, and special interventions
for this group of clients offered in the reporting country. The full details can be found in the
national REITOX reports prepared by the respective National Focal Points.
31
Prevalence
Problem cannabis use has been defined by the majority of countries through daily or nearly
daily use of the substance. In some cases ICD-10 or DSM-IV clinical classifications were
used. Most countries fall in the range of 0,2-3,0%. Less problematic patterns of use are more
frequent. PCU is much more spread in special settings like prisons or youth help centres
(Table 6).
Table 6: Prevalence of problematic cannabis use (PCU) in Europe
Country
Comments
Austria
regular use, age group 15+
use once per week,
age group 12-25
Prevalence
4,6%
Male: 14,7%
Female: 7,1%
Belgium
--
Czech Republic
--
Denmark
constant users suffering from physical, social, mental
damage
N=6.000
Finland
use during last 30 days
France
(almost) daily use within last 2 weeks, age group 17-75
Germany
Cannabis dependence (DSM-IV), age group 14-24, lifetime
prevalence
0,9%
dependence, age group 18-59, last year prevalence
0,2%
Greece
3%
abuse, age group 14-24, lifetime prevalence
4%
used when alone
9%
problems through cannabis use (self-report)
Ireland
1%
N=40.000
17% cannabis abusers in clinical group with primary
schizophrenic disorder
~ 1%
--
Italy
--
Lithuania
--
Luxembourg
--
Netherlands
Cannabis dependence (DSM-IIIR) age group 18-64 years,
last years prevalence
Netherlands
Problem youth in Rotterdam, age 14-17, cannabis use during
11+/30 last days and having related problems
Norway
used cannabis more than 10 times in the last 6 months
3%
Portugal
Daily use among prison population
6%
Slovenia
Used cannabis more than 40 times in lifetime, age-group_
15-16 (ESPAD), used cannabis during the last 12 months
2%
Spain
daily use during last 12 months
2%
weekly use during the last 12 months
4%
Sweden
United Kingdom
0,3-0,8%
20%
-cannabis dependence only, age group 16-74
3%
32
Treatment demand
Data on treatment demand are not really complete and some of the countries can describe
the situation only through highly selective samples of treament facilities. From 19 (future)
member states reporting, only two reported a reduction in prevalence over the last 10 years.
5 counties cannot give an indication on trends, but 13 member states reported an increasing
trend (Table 7).
Table 7: Demand for treatment for PCU in Europe
Country
Prevalence
Type
Trend
Comments
over 10
years
Austria
20-25% use cannabis OR
hallucinogens (2001)
Out
?
national survey per
treatment units
Austria
very rare
18 cases dependence, 45 cases of
abuse (ICD9) (2002)
In

almost always linked
with mental
disorders
Belgium
--
Czech
Republic
751 cases with main drug cannabis
(2002)
All
?
Denmark
21% of treatment demands (2002)
All

Finland
18% of treatment demands (2002)
-

France
23% of treatment demands (2002)
All

Germany
27% of treatment demands (2002)
Out

Percentage or drug
users treated
Greece
7% of treatment demands (2002)
Out

decrease since 1999
Ireland
15% of treatment demands (2000)
All

Italy
8% of treatment demands (2001)
All

Lithuania
6% of treatment demands (2000)
Out
?
Luxembourg
11% of treatment demands (2002)
All

Netherlands
24% of treatment demands (2002)
Out

Percentage of drug
users treated
Norway
9% (females), 16% (males) of
treatment demands (2001)
All

Percentage of drug
users treated
Portugal
extremely small number (2003)
All
?
expert opinion
Slovenia
8% of treatment demands (2002)
All

Spain
7% of treatment demands (2001)
All

Sweden
50% of clients below 20 years, 27% of
clients above 20 years of age
All

United
Kingdom
9% of treatment demands in England,
7% in Scotland use only cannabis
All

?
City of Prague
Great regional
variation, regional
trend reported
expert opinion
 = increase,  = decrease;  = unchanged; ? = not available
33
Characteristics of problem cannabis users
Despite very different treatment settings all over Europe, clients share some common
characteristics: 74-90% of the clients are male, in most countries the biggest age-group is 20
to 25 years. The big percentage of cannabis users still goes to school and lives with the
parents. Problem cannabis users visit the treatment centre because of problems with family,
school or work-place, addiction problems or other psychiatric disorders. By far the majority of
cannabis users is well integrated into family, school or working-place (Table 8).
Table 8: Characteristics of PCU clients in treatment in Europe
Country
Characteristics
Austria
Gender: primary males
Socio-economic state: socially integrated
Problems: often psychotic disorders
Belgium
--
Czech Republic
Gender: 74% male
Age: 62% between 15 and 20 years,
Drug use: 51% use cannabis not more than 2 years
Problems: 39% parents; 30% discipline, 23% school
Denmark
Gender: 81% male
Age: males: 26 years, females: 28 years
Socio-economic state: 54% receive cash benefits, 10% daily benefits
Problems: handling daily activities, average marks and absence from school
Finland
Gender. 79% male
Age: 20,2 years
Education: 70% primary level
Socio-economic state : 29% unemployed
Drug use: 40% 2nd problem substance alcohol, duration of C. use: 5 years
Problems: depression, school attainment, psychoses
France
Gender: 82% male
Age: 25,5 years
Drug use: 40% have a 2nd problem substance, in most cases alcohol
Problems: social achievements (school, work)
Germany
Gender: 82% male
Age: main age group 18-25 years
Drug use: 22% have alcohol as a 2nd problem substance, 20% ecstasy
Problems: social achievements (school, work)
Greece
Gender: 88% male
Age: mean 23 years
Socio-economic state : 81% live with their family, 33% unemployed
Problems: Psychiatric comorbidity
Ireland
Gender: 85% male
Italy
--
Lithuania
Problems: depression, mood disorders
Luxembourg
Problems: 33% had previous demands for psychiatric treatments
Netherlands
Gender: 80% male
Age: 85% older than 20
Drug use: most have problems also with other substances, biggest increase for
single users and users with cannabis plus alcohol problems
Problems: Increased 12 months prevalence of cannabis use for people with mood
disorders (7,1%), mixed mood/anxiety disorders (8,8%) compared to people
without such disorders (3,2%)
Norway
Problems: younger ones “dropping out” of family, school and social context, older
clients show more often mental problems: anxiety/ depression/ general antisocial
behaviour, Increased problems at school and workplace
Portugal
Problems: Amotivational syndrome and psychoses are frequent
Age: Start of drug use at 15, begin treatment at 20
(outside Greater Dublin)
34
Table 8: Characteristics of PCU clients in treatment in Europe (continued)
Slovenia
Gender: 68% male
Age: 19 years (first treatment demanders)
Drug use: 66% used cannabis daily for the last 6 months
Spain
Gender: 90% Age: begin use at 16, start treatment at 24 years
Drug use: 58% used alcohol during the last 30 days, 43% cocaine
Problems caused by cannabis: accidents 40%, missed class 41%, economic
problems 33%, conflicts with family 30%, difficult at work 30%
Sweden
Dysfunctional family background
Drug use: get drunk on a regular basis, 20% use additional drugs as well
United Kingdom
Males: 75%
Age: 30-40% below 20 years
Treatment needs and referrals
Between 19 and 44% or the clients come by themselves without the activities of any other
person or institution. Where an comparison between the age-groups above and below 20
years was made, the percentage of self-referred clients is considerably higher in the older
group of clients.
Parents, family and friends are important mediators and motivators when it comes to
treatment. Between 26 and 90% of the clients have been referred by these persons when
they come to drug treatment.
Referral through judicial proceedings or police interventions is of specific interest as there
has been the hypotheses, that a growing pressure through law enforcement has created the
increase in treatment demands for cannabis related problems. While law enforcement is an
important actor, in most countries only 20-30% of all clients enter treatment this way. Only
Austria reports a much higher percentage for a subset of treatment facilities which are
reporting to the national level. No country draw the conclusion from there national data, that
changes in law or legal practice were sufficient to explain the increase in treatment demands
found (Table 9).
35
Table 9: Treatment needs and referral for PCU clients in Europe
Country
Treatment needs and referral
Information basis
Austria
Many do not need medical treatment or
psychosocial care for cannabis use
Expert opinion
Austria
¾ of clients referred to by authorities
Assessment
Austria
Mixing users with opiate addicts and poly drug
users very problematic
Expert opinion
Belgium
--
Czech Republic
Referral: 40% self referred, 30% family
Treatment statistics
Denmark
Different from traditional treatment institutions and
heroin addicts, additional problems besides drugs
Expert opinion
Finland
Referral: 19% self referred, 26% family/friends
Treatment statistics
France
Referral: 24% result of judicial proceedings
Treatment statistics
Germany
Referral: 25% of males, 20% of females comes as
a result of judicial procedures or by order of public
authorities
Treatment statistics
Greece
Referral: 19% self referred, 57% family/friends
Treatment statistics
Ireland
Referral: 44% self referred/family /friends, 22%
court/ probation/ police
Treatment statistics
Italy
--
Lithuania
Referral: majority through police (driving under
influence of drugs), parents
Expert opinion
Luxembourg
Referral: Parents/school most frequent
Study
Netherlands
most problem cannabis users avoid the
specialised drug treatment centre for unknown
reasons
Treatment statistics
referrals (<20 years): 35% self referred, 19%
familiy/ friends, 9% Justice
referrals (>=20 years): 42% self referred, 3%
familiy/ friends, 14% Justice
Norway
--
Portugal
--
Slovenia
--
Spain
--
Sweden
gender: <20years: 60% male, >=20: 80% male
referrals (<20 years): 90% family/ friends, 6%
school, 4% social welfare
referrals (>=20 years): 43% self referred, 18%
family/ friends, 21% social welfare, 5% justice
United Kingdom
Referral: 26-29% self referred, 4-9% family
/friends, 12-23% GPs/primary care
teams/psychiatrist, 7-9% probation/police
36
Specific treatment offers for problem cannabis users
In most cases for the treatment and care of problem cannabis users standard procedures
and programmes are applied. In some cases, however, it has been criticised that mixing up
cannabis clients with heroin users in treatment might not be the most efficient way to treat
this group.
In addition to that a number of more specific approaches have been mentioned, which should
be looked at and evaluated in more depth in future to develop more efficient methods of
treatment for this specific clientele. Some elements can be grouped in the following way.

Short-term treatments
A very limited number of contact (up to about 5) are used for information, develop risk
perception and risk competence, or should help to quit smoking cannabis

Integrative interventions
Elements of secondary prevention play an important role in some interventions which
can be characterised by a intensive cooperation between different institutions (youth
help, drug help, law enforcement)

Peer education
In a number of cases elements of peer education play an important role to better
reach problem cannabis users but also to offer help and support to this group despite
a lack of adequate public funding.
Beside these specific interventions the reports mention that treatment of cannabis related
problems is also taking place within standard health care. The British report underlines, that
GPs as well as (tobacco) smoking cessation programmes do see and treat a considerable
number of cannabis users.
37
Table 10: Special treatment offers for PCU in Europe
Country
Treatment provision
Austria
Short term counselling programme (max. 5 contacts)
Information and increased risk competence through peer education
Belgium
--
Czech Republic
Denmark
Combined social services and interventions
Municipal dedicated peer teams for very young cannabis users
Finland
Acupuncture for cannabis users with depression disorder
France
No special institutions, but specific programmes. Multi partnership project
outside the field of drug treatment
Germany
Peer education for driving licence groups
Greece
Counselling unit for adolescent drug users (KETHEA) integerating
counselling, community intervention, social support and family support
Ireland
--
Italy
--
Lithuania
--
Luxembourg
MSF youth solidarity project: intervention team in collaboration with youth
magistrate and law enforcement
Netherlands
Ongoing review of existing treatment programmes
Self-help internet programme
Norway
6-weeks course: Smoking cessation for cannabis users to “free young
people’s resources”
Portugal
under discussion
Slovenia
--
Spain
no specific interventions
Sweden
Manual based cognitive behavioural therapy for cannabis users
United Kingdom
Use of general health care: 25% of 20 GPs in Inner London researched
in 2001 treated cannabis problems within the last 4 weeks
smoking cessation programmes used: 24% of clients in a smoking
cessation clinic hat used cannabis during the last 4 weeks
38
7 Recommendations for research and methodological
developments for assessment at European level
Options for assessment
An increase in prevalence of cannabis use has been found in most EU member states during
the last years (EMCDDA 2003). The trend for problem cannabis use (PCU) is not totally clear
due to a lack of common standards of data collection and reporting. There are several ways
to assess problem cannabis use:

Assessing PCU through high frequent of use
For this purpose items can be used which are already included in the EMCDDA
model questionnaire for population surveys. A cut-off value for the frequency of
cannabis use for the last 12 months should be set for PCU, which would make
comparisons between countries easier.

Assessing PCU through qualitative aspects of use: dependence/ harmful use/
abuse
The criteria for harmful use or dependence correlate with frequency of use, but target
negative consequences instead of patterns of use. For both aspects EMCDDA
standards have not been defined yet, but existing instruments could be used. The
CIDI has been used in a number of international studies as an instrument for
personal interviews and its items also have been applied successfully in selfadministered questionnaires.
Possible sources of information
The relevant information could be drawn from a number of data sources:

Surveys
The items should be integrated in surveys or administered separately
standardised way in the population or in treated groups.

in a
Treatment demand statistics
A qualified description of persons with PCU can be produced with little effort by
treatment facilities based on the concept of main drug (TDI). As only a minority of
persons with PCU are seen by specialised treatment facilities, this indicator can
deliver information on trends and characteristics of PCU but not on the prevalence.

Research studies
A more reliable way to produce diagnoses is based on personal interviews. While in
this way a high data quality can be reached for example through the application of
CIDI, costs and efforts are rather high as well. This solution seems reasonable for
research purposes but not adequate for monitoring purposes.
39
Proposals for methodological development
From a number of possible actions two are proposed, which seem especially important and
cost-effective:
1. The TDI at the moment offers some helpful information on treated cannabis clients.
While the standards have been widely accepted and are applied in most countries, in
some areas there is still only a limited level of standardisation given. The definition of
“primary drug” in treatment until now can be implemented in the Member States in
different ways and in fact only a small number of country explicitly follows the
international standards ICD-10 or DSM-IV. This is a possible risk for comparability
with not empirical evidence to judge its size. A recent German study has shown
reasonable good quality of diagnosis for primary cannabis related cases (Simon &
Sonntag, in print), but as the German system is based since 10 years on ICD-10
standards this does not answer the question for other countries.
Therefore diagnostic procedures should be defined more precise in addition to the
TDI standards taking into account the diagnostic criteria of ICD/DSM in order to
produce prevalence data on the basis of international diagnostic standards. This
should take place at least for subsets of treated clients in every member state. A
small research study in a representative sample of countries should check on the
basis of a limited number of clients (N=50 per country) intercorrelation between
classification as usual and classification on the basis of a more rigorous definition
following ICD/DSM.
2. Existing screening instruments should be further developed to come up with a simple
but sensible instrument, which can classify cannabis users on the basis of drug use
patterns in two or three groups according to the degree of risk or problems bound to
their drug use. This instrument could at the same time serve as a screening
instrument in drug treatment in order to find the most applicable intervention for each
cannabis users asking for help and collect epidemiological data within surveys and
treatment monitoring.
In order to increase cost-effectiveness it should be discussed if such an action could take
into account also other substances like amphetamines, ecstasy and cocaine, which also play
a big role in recreational use of drugs on one side and can be cause of problems and
treatment needs on the other side.
40
8 Bibliography
8.1
Assessment
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Buchan, B.J., Dennis, M.L., Tims, F.M., Diamond, G.S. (2002). Cannabis use: consistency and validy
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Cummins, L.H., Chan, K.K., Burns, K.M., Blume, A.W., Larimer, M., Marlatt, G.A. (2003). Validity of
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Dilling, H., Mombour, W. & Schmidt, M.H. (Hrsg.) (1999). Internationale Klassifikation psychischer
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