biological approach to explaining OCD

• Genetic explanations


  Some mental disorders appear to have a stronger biological component than others, and OCD is a good example of a condition that may be largely understood as biological in nature
• Genetic explanation of OCD


  • Aubrey Lewis, conducted a classical study on OCD patients 37%. Had parents with a OCD and 21% had siblings.

  • Suggest that OCD runs in the family, although genetic vulnerability is passed on from one generation to another not the certainty of OCD.
• diathesis stress model


  Certain genes leave some people more likely to develop a mental disorder, but is not certain. Some environmental stress is necessary to trigger the condition.
• Candidate genes


  • genes involved in regulating the development of the serotonin system.

  • E.g. the gene 5HT1 – D beta is implicated in the transport of serotonin across synapses.
• OCD is polygenic


  • OCD is not caused by one singular gene, but a combination of genetic variation that together significantly increase vulnerability.

  • up to 230 genes are involved in OCD.
• different types of genes

  One group of genes may cause OCD in one person, but a different group of genes may cause the disorder in another. (aetiologically heterogenous)
• strength of genetic explanations for OCD

  • Strong evidence base

  • evidence from a variety of sources, which strongly suggest that some people are vulnerable to OCD as a result of their genetic make up.

  • Gerald nestadt review twin studies and found 68% of identical twins shared OCD as opposed to 31% of non-identical twins.

  • Suggest that there must be some genetic influence of the development of OCD.
• limitation of genetic model of OCD

  • Environmental risk factors

  • OCD doesn’t appear to be entirely genetic and seems that environmental risk factors can also trigger or increase the risk of developing OCD.

  • Kiara Cromer did a study and found that over half the OCD clients in the sample have experienced a traumatic event in the past, which shows that OCD is more severe in those with trauma.

  • Means that genetic vulnerability only provides a partial explanation for OCD.
• Neural explanations


  The genes associated with OCD are likely to affect the levels of key neurotransmitters as well as structures of the brain
• Serotonin


  A neurotransmitter believed to help regulate mood
• Low levels of serotonin

  Normal transmission of mood-relevant information does not take place and a person may experience low moods (and other mental processes may also be affected)
• Decision-making systems


  Some cases of OCD, and in particular hoarding disorder, seem to be associated with impaired decision-making
• Frontal lobes


  The front part of the brain (behind your forehead) that are responsible for logical thinking and making decisions
• Abnormal functioning of the lateral (side bits) of the frontal lobes of the brain


  May be associated with impaired decision-making in some cases of OCD and hoarding disorder
• Left parahippocampal gyrus


  An area associated with processing unpleasant emotions, functions abnormally in OCD
• strength of the neutral model of a OCD


  • Existence of some supporting evidence.

  • OCD symptoms form part of conditions that I need to be biological such as the degenerative brain disorder Parkinson’s disease.

  • If a biological disorder produces OCD symptoms, then we may assume the biological processes underline OCD.

  • Suggest a biological factors may be responsible for OCD.
• limitation of the neutral model


  • serotonin OCD link may not be unique to OCD.

  • Many people with OCD also experience clinical depression (Co-morbidity).

  • This depression probably involves, disruption to the action of serotonin, which leaves us with a logical problem, when it comes to serotonin as a possible bases for OCD.

  • This means that serotonin may not be relevant to OCD symptoms.