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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)

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Models of Psychopathology

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  1. Models of Psychopathology

  2. 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)

  3. 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

  4. 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

  5. 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;

  6. Research Designs contd. • Twin method: Compare MZ with DZ twins • Family method • Adoptions method • Twins Reared Apart

  7. 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

  8. 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

  9. 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

  10. 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

  11. Early Markers contd. • Clinical symptoms • More likely to have higher psychoticism scores earlier in adulthood

  12. 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

  13. Model for Schizophrenia

  14. Mediators/Moderators • Require at least three variables—predictor, criterion and intervening

  15. 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

  16. Moderator examples

  17. 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

  18. Mediator Examples

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