10. explaining OCD

what approach explains OCD

biological approach - a perspective that emphasises the importance of physical processes in the body such as genetic inheritance and neural function

what are the two biological explanations for OCD

1. genetic explanations - candidate genes, polygenic, different types

2. neural explanations - serotonin, decision making systems

study on genetics

genes are involved in individual vulnerability to OCD

lewis observed that of his OCD patients, 37% had parents with OCD and 21% had siblings with OCD - suggests it runs in families

although what is probably passed on is genetic vulnerability and not the certainty of OCD

diathesis stress model

according to it, certain genes leave some more likely to develop a mental disorder but it is not certain - some environmental stress (experience) is necessary to trigger the condition

candidate genes

• researchers have identified genes which create vulnerability for OCD called candidate genes

• some are involved in regulating the development of the serotonin system

example of a candidate gene

SERT gene

• affects serotonin transport

• lower levels are implicated in OCD

• plays a role in mood balancing which in turn may help regulate obsessive thoughts

polygenic nature

• OCD seems to be polygenic

• means it is not caused by one single gene, but by a combination of genetic variations that together significantly increase vulnerability

study on polygenic nature

• taylor has analysed findings of previous studies and found evidence that up to 230 genes may be involved in OCD

• genes have been studied in relation to OCD include those associated with the action of dopamine as well as serotonin, both neurotransmitters believed to have a role in regulating mood

different types of OCD

• one group of genes may cause OCD in one person but a different group of genes may cause the disorder in another person

• term to describe this is aetiologically heterogeneous

• also some evidence to suggest different types of OCD may be the result of particular genetic variations

genetic explanation summarised

• genes make up chromosomes and consist of DNA which codes the physical features of an organism and psychological features

• genes are transmitted from parents to offspring, inherited

neural explanations

• view that physical and psychological characteristics are determined by the behaviour of the nervous system, in particular the brain as well as individual neurons

role of serotonin

• neurotransmitter serotonin is believed to regulate mood

• neurotransmitters are responsible for relaying information from one neuron to another

• if a person has low levels of serotonin then normal transmission of mood relevant information does not take place and a person may experience low moods

role of dopamine

• DA activity in the DSM has been linked to the development of compulsive behaviours

• neural circuits connecting cerebral cortex to DSM are thought to control movement and reward seeking behaviours

• high DA levels in the DSM increase compulsive reward seeking

decision making systems

• some cases of OCD are associated with impaired decision making which in turn may be associated with abnormal functioning of the lateral of the frontal lobes of the brain (responsible for logical thinking and making decisions)

• also evidence to suggest the left parahippocampal gyrus (processes unpleasant emotions) functions abnormally in OCD

genetic explanations evaluation

1. research support

2. environmentally reductionist

research support

• plethora of research support 

1. LEWIS found that of his OCD patients, 37% had parents and 21% had siblings with OCD

2. MARINI ET AL found a person with a family member diagnosed is around 4x as likely to develop it as someone else 

• suggests a strong genetic influence on OCD

environmentally reductionist

• diathesis stress model suggests genetics create a vulnerability to OCD but environmental stressors (eg trauma or life events) trigger its development 

• supported by CROMER ET AL who found over 50% of OCD patients experiences trauma in the past

• highlights biological factors alone cannot fully explain OCD

neural explanation evaluation

1. research support

2. correlation and causality

3. fMRis

4. SSRIs

research support

• biological evidence supports neural explanations

• antidepressants that target serotonin reduce OCD symptoms suggesting seratonin may be involved in OCD - suggests it has a biological basis, particularly involving neurotransmitters and brain structures

• neural model is supported by real world uses

correlation and causality

• correlations between brain abnormalities and OCD do not prove causation

• brain dysfunction is linked to OCD, but it is unclear whether this causes OCD or is a result of it - a third factor eg stress may influence both brain function and OCD

• without casual evidence, neural explanations remain uncertain

fMRIs

although a sophisticated apparatus, its not 100% evidence of neurotransmission

• brain activity may be as a result of other factors like nervousness from being in the machine

• not yet possible to track and measure live neurotransmission

only can claim that OCD has neurological correlates rather than causation

SSRIs

• not all OCD sufferers respond positively to SSRIs

• means neural may not be the sole cause

• reducing external validity