Biological approach to explaining OCD

• Genetic explanation

  = Genes make up chromosomes and consist of DNA which codes the physical and psychological features.

  • 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.
  • So suggests OCD runs in families and what is passed on= genetic vulnerability not the certainty of OCD.
• Diathesis stress model

  = Certain genes leave some people more likely to develop a mental disorder, some environmental stress is necessary to trigger the condition.
• Candidate genes

  = Create vulnerability for OCD.

  • Some are involved in regulating the development of serotonin systems.
• OCD is polygenic

  -OCD is not caused by one single gene but by a combination of genetic variations that together increase vulnerability.

  -Taylor found evidence that up to 230 different genes may be involved in OCD.

  -Genes studied in relation to OCD include those associated with the action of dopamine and 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 may cause the disorder in another person.

  • A etiologically heterogenous= the origins of OCD vary from one person to another.
  • Also evidence to suggest that different types of OCD may be the result of particular genetic variations.
• Evaluation- research support

  There's evidence which strongly suggests that some people are vulnerable to OCD as a result of their genetic make-up.

  • Twin studies= Nestadt et al found that 68% of identical twins shared OCD as opposed to 31% of non-identical twins.
  • Family studies= a person with a family member diagnosed with OCD is around 4 times more likely to develop it as someone without.
  • Suggests there must be some genetic influence on the development of OCD.
• Evaluation- environmental risk factors

  Limitation

  • OCD does not appear to be entirely genetic in origin, environmental risk factors can also trigger or increase the risk of developing OCD.
  • Cromer et al found that over half the OCD clients in their sample had experienced a traumatic event.
  • OCD more severe in those with 1 or more traumas.
  • So genetic vulnerability only provides a partial explanation for OCD.
• Neutral explanation

  = View that physical and psychological characteristics are determined by the behaviour of the nervous system, in particular the brain and individual neurones.
• Role of serotonin

  Neurotransmitter serotonin believed to help regulate mood.

  • Neurotransmitters are responsible for relaying information from one neurone to another.
  • If a person has low levels of serotonin then normal transmission of mood-relevant information doesn't take place and a person may experience low moods.
  • Som cases of OCD may be explained by a reduction in functioning of the serotonin system in the brain.
• Decision making systems

  Some cases of OCD (hoarding disorder) seem to be associated with impaired decision making- may be associated with abnormal functioning of the lateral frontal lobes.

  • Frontal lobes are responsible for logical thinking and decision making
• Evaluation- research support

  Antidepressants that work purely on serotonin are effective in reducing OCD symptoms and this suggests that serotonin may be involved in OCD.

  • OCD symptoms form part of conditions that are known to be biological in origin eg: Parkinson's disease which causes muscle tremors and paralysis.
  • If a biological disorder produces OCD symptoms then we may assume the biological processes underlie OCD
  • Suggests biological factors may also b responsible for OCD.
• Evaluation- no unique neural system

  Limitation= the serotonin- OCD link may not be unique to OCD

  • Many with OCD also experience clinical depression= co-morbidity.
  • This depression probably involves disruption to the action of serotonin.
  • Problem= serotonin as a possible basis for OCD
  • Could also be that serotonin actively disrupted in people with OCD because they also depressed.
  • So serotonin may not be relevent to OCD symptoms