This document contains revision notes for biological explanations of ocd for the psychopathology topic in paper 1 of psychology AQA A level. All content follows the AQA specification.
FAMILY STUDIES
● Genes are involved in individual vulnerability to OCD.
● Lewis: 37% of OCD patients had parents with OCD and 21% had siblings with OCD.
● OCD runs in families, genetic vulnerability is passed on not the certainty of OCD.
THE DIATHESIS (genetic predisposition) - STRESS (environmental trigger) MODEL
● Shows certain genes leave people more likely to suffer a mental disorder but it is not
certain, some environmental stressor has to trigger it.
● If genetics have influence on behaviour, this is moderated by the effects of the
environment.
CANDIDATE GENES
● Researchers have identified candidate genes that create a vulnerability for OCD.
Some of these genes are involved in regulating the development of serotonin systemic.
OCD IS POLYGENIC (involves several genes)
● Taylor: analysed the findings of previous studies and found evidence that up to 230
different genes may be involved in OCD.
● These genes are associated with the action of dopamine and serotonin,
neurotransmitters have a role in regulating mood.
Evidence shows different types of OCD may be due to particular genetic variations.
Aetiologically heterogeneous: the origin of OCD has different causes.
THE ROLE OF SEROTONIN
● Serotonin helps regulate mood. Neurotransmitters are responsible for sending info
between neurons. Low levels of serotonin mean normal transmission of mood
relevant information does not take place and mental processes are affected.
● OCD can be explained by a reduction in the functioning of the serotonin system.
DECISION-MAKING SYSTEMS
● Some cases of OCD are associated with impaired decision making. Associated with
abnormal functioning on the lateral of the frontal lobe in the brain.
● The left parahippocampal gyrus (processing of unpleasant emotions) functions
abnormally in OCD.
STRENGTH: Effective
P: Evidence that some people are vulnerable to OCD due to their genetic make-up.
E: Nestadt et al. reviewed previous studies, 68% of identical twins shared OCD as opposed
to 31% of non-identical twins.
J: Suggests a genetic influence on OCD.
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