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