OCD - biological explanation

Question 1

Genetic explanations

Answer 1

• Of his OCD patients, 37% had parents with OCD and 21% had siblings with OCD
• Suggests OCD runs in families - but what is passed on is genetic vulnerability not OCD
• According to diathesis stress model certain genes leave some people more likely to develop a mental disorder but it isn’t certain - some environmental stress is necessary to trigger the condition
• Candidate genes - certain genes create vulnerability for OCD - some of these genes involved in regulating development of serotonin system
• OCD is polygenic - means OCD is caused by many genes not just one - they together increase vulnerability - up to 230 different genes may be involved in OCD
• Different types of OCD - one group of genes may cause OCD in one person a different group of genes may cause the disorder in another person - term to describe this is aetiologically heterogeneous means that origins of OCD vary from one person to another

Question 2

Neural explanations

Answer 2

• The role of serotonin - a neurotransmitter which is believed to help regulate mood - neurotransmitters are responsible for relaying information from one neurone to another - low level of serotonin then normal transmission of mood relevant information doesn’t take place so person may experience low moods - some cases of OCD may be explained by a reduction in the functioning of serotonin system in the brain
• Decision making systems - some cases of OCD may be associated with impaired decision making - could be associated with abnormal functioning of the lateral of frontal lobes of the brain - frontal lobes are responsible for logical thinking - evidence to suggest that the left parahippocampal gyrus, is associated with processing unpleasant emotions

Question 3

Genetic explanations - Strength

Answer 3

• Strong evidence base
• People are vulnerable to OCD as a result of their genetic makeup
• Source of evidence is twin studies - found that 68% of identical twins shared OCD as opposed to 31% of non-identical twins
• Suggests there must be some genetic influence on the development of OCD

Question 4

Genetic explanations - Limitation

Answer 4

• There’s also environmental risk factors
• OCD does not appear to be entirely genetic in origin and it seems that environmental risk factors can also trigger or increase the risk of developing OCD
• Means that genetic vulnerability only provides a partial explanation for OCD

Question 5

Neural explanations - Strength

Answer 5

• Some supporting evidence
• Antidepressants that work purely on serotonin are effective in reducing OCD symptoms - suggests serotonin may be involved in OCD
• OCD symptoms form part of conditions that are biological in origin, e.g Parkinson’s disease, which causes muscle tremors and paralysis
• If a biological disorder produces OCD symptoms, we may assume the biological processes underline OCD
• Suggests that biological factors may also be responsible for OCD

Question 6

Neural explanations - Limitation

Answer 6

• Serotonin OCD link may not be unique to OCD
• Many people with OCD also experience clinical depression (co-morbidity)
• This depression might involves disruption to action of serotonin
• Leaves us with a logical problem when it comes to serotonin as a possible basis for OCD
• Could simply be that serotonin activity is disrupted in many people with OCD because they are depressed as well
• Means serotonin may not be relevant to OCD symptoms