Eval of Genetic OCD

• Genetic explanation for OCD


  • Strong evidence base
  • Variety of sources strongly suggest some people are vulnerable to OCD due to genetic make-up
• Evidence from twin studies


  • Nestadt et al. (2010) found 68% of identical twins (MZ) shared OCD vs 31% of non-identical twins (DZ)
• Evidence from family studies

  • Person with family member diagnosed with OCD is around 4 times as likely to develop it
• Purely genetic explanations overlook the role of the environment as a cause of OCD characteristics
• Child has around 11% chance of developing OCD if one of their parents has the condition, despite inheriting 50% of their genes
• Environmental influences on OCD


  • Over half of OCD patients had a traumatic experience, and OCD was more severe with more than one trauma
• Diathesis-stress model

  May be beneficial to explain the origins of OCD as a complex interaction of nature and nurture
• OCD is unlikely to be caused by a single candidate gene, it is more likely a combination of genes (e.g. COMT and SERT)
• Psychologists have been unsuccessful at identifying all the genes involved and there is a lack of consistency in research findings regarding specific genes related to OCD
• Each genetic variation only increases the risk of OCD by a fraction, so a genetic explanation is unlikely to ever be useful because it provides little predictive value
• Further research is needed to investigate the idea that OCD is a heritable condition, as few details are fully understood about the actual genetic mechanisms underpinning the disorder
• Different genetic factors may contribute to different subtypes of OCD (e.g. hoarding, tic-related)
• Genetic factors in OCD subtypes


  • Hemmings et. al. found a defect in a gene for dopamine was much less common in people with early onset than late onset OCD
• More focused research is needed to fully understand the role of genes in explaining OCD