Download Models of Psychopathology

Models of
Psychopathology
Examining the Diathesis
► Classic
Question: Which is more important,
heredity or environment? (main effects model)
► Evolution to: both are important, they both
influence one another (essentially the
interactionist model)
► New concept: nature and nurture anre intricately
connected; rather than asking which is more
important, how do nature and nurture interact to
produce behavioral development. (essentially an
interactive multiplicative model)
Interactive/Multiplicative
► Nature
and nurture are both fully involved in
providing a source of any behavioral
development;
► They can not function in isolation;
► Their interaction is multiplicative; the
presence of each source is intertwined with
the presence of the other source; the
product of the nature/nurture interaction;
► This is the transactional model
More nature/nurture
► Nature
never affects behavior directly; always in
the context of an environment;
 We don’t inherit behavior; we inherit DNA
 Genes place constraints on behavioral development but
we don’t always know the extent of the constraints
► Environment
never directly produces behavior; it
shows variations in effects depending on the
heredity-related characteristics of the organism;
 Environments can be internal or external
Research Designs
► Children
and parents share 50% of genes
► Siblings share 50% of their genes on
average;
► Fraternal of DZ twins share 50% of their
genes;
► MZ twins share 100% of their genes;
Research Designs contd.
► Twin
method: Compare MZ with DZ twins
► Family method
► Adoptions method
► Twins Reared Apart
Diathesis-Stress Models
► Diathesis:
A constitutional disposition or
predisposition to some anomalous or morbid
condition, ‘which no longer belongs within the
confines of normal variability, but already begins
to represent a potential disease condition’
 All suggest a vulnerability, necessary but not sufficient
 All serve as an antecedent to the pathological condition
 All disorders are polygenic
Biological Variables
► Biological
Variables differ in their stability over
time;
► Vulnerability Marker: a biological characteristic
that does not change with the disorder;
► Episode Marker: Abnormal during the acute stage
of the disorder but change back to normal when
the patient is recovered;
► Mediating vulnerability marker: Deviant during
remission but even more abnormal during
episodes
Transmission of Schizophrenia Risk: An
example of diathetic complexity
► Schizophrenia
in mothers is a generalized rather
than specific risk for psychiatric illness;
 In one study 1/5 developed a psychotic disorder
(including schizophrenia)
 1/5 developed schizotypal personality disorder
 ¼ developed some other psychiatric disorder
► There
is an interplay among the biological,
psychological and social-contexual aspects of
normal and abnormal lifespan development
Early Markers
► Developmental
abnormalities in at risk
children (HRsz) are early risk indicators of
schizophrenia;
► Social and emotional difficulties
 Some evidence for increased emotional
problems and poorer social competence
► Neurodevelopmental
problems
 Impairments seen in sustained attention
 Boys were much more vulnerable
Early Markers contd.
► Clinical
symptoms
 More likely to have higher psychoticism scores
earlier in adulthood
Methodological Issues
► Small
samples
► Unrepresentative samples
► Adopted away children may be more
vulnerable
► HRsz children are often exposed to a range
of advere envioronmental influences
► Many mothers with schiz also have
depression
Model for Schizophrenia
Mediators/Moderators
► Require
at least three variables—predictor,
criterion and intervening
Moderator
► Specifies
the conditions under which a given
effect occurs and well as the conditions
under which the direction or strength will
vary
► Often fixed like sex, race or class
► It is an interaction effect
► The nature of the impact depends on the
value of the moderator
Moderator examples
Mediator
► Specifies
how (or the mechanism by which) a
given effect occurs
► The independent variable ‘causes’ the second
variable which then causes the outcome
► The relationship between the predictor and
outcome is reduced to nonsignificant with the
addition of the mediator
► Initially the predictor and outcome need to be
correlated
Mediator Examples