The Biological Approach to Explaining OCD

• The genetic explanation, through the diathesis-stress model, suggests that some have a genetic vulnerability towards developing OCD.
• Lewis et al. found that of his OCD patients, 37% had parents with OCD and 21% had siblings with OCD.
• OCD is polygenic, meaning that up to 230 different genes are involved in its development (Taylor).
• The genes involved are often associated with the functioning of neurotransmitters, such as dopamine and serotonin, both associated with regulating mood.
• Researchers have identified candidate genes which increase a person’s vulnerability towards developing OCD.

  • One of these is 5HT1-D beta, which is implicated in the efficiency of serotonin transport across synapses.
• OCD is also aetiologically heterogenous, meaning that its origin has many different causes.

  • For example, it has been suggested that hoarding disorder is caused by a particular genetic variation.
• STRENGTH OF OCD EXPLANATIONS:

  Supporting evidence

  • Nestadt et al. reviewed previous twin studies of OCD and found that 68% of identical twins, compared to 31% of non-identical twins, share OCD.
  • This strongly suggests that there is a genetic basis for this disease because identical twins share 100% of their genes with each other, whilst dizygotic twins only share 50% of genes with each other.
• It is important not to be deterministic - just because an individual has a particular combination of candidate genes does not mean that the individual is ‘doomed’ to develop OCD, but rather that this genetic vulnerability must be paired with an environmental stressor to result in OCD, as dictated through the diathesis-stress model.
• WEAKNESS OF OCD EXPLANATIONS:

  Too many candidate genes

  • With over 230 candidate genes each individually coding for an increased risk of OCD, then this poses a practical issue in that it is difficult to assess which candidate genes have the greatest influence and so which genes drug treatments should target.
  • Thus, such an explanation is likely to have little predictive value in the future.
• 2. WEAKNESS OF OCD EXPLANATIONS:

  Ignores environmental factors

  • Cromer et al. found that of his OCD patients, over half had experienced a trauma in their lives, and that there was a positive correlation between an increasing number of traumas and the increasing severity of the OCD which patients suffered from.