Genetic explanation for OCD

• Lewis (1936) observed that of his OCD patients, 37% had parents with OCD and 21% had siblings with OCD. This suggests that there is a genetic factor and that OCD could be heritable.
• What are candidate genes and what do they show about OCD?

  Genes found to be more prevalent in OCD people.

  Taylor (2013) analysed previous studies and found evidence that up to 230 genes may be involved in OCD (it is polygenic)
• What is a strength for the genetic explanation of OCD?

  Nestadt (2010) reviewed twin studies and found that 68% of MZ twins shared OCD compared to 31% of DZ twins: this suggests a genetic basis because the degree of concordance is significantly higher in MZ twins than DZ twins
• What is a limitation for the genetic explanation of OCD?

  Environmental risk factors: Cromer (2007) found over half of people with OCD had experienced past trauma, and the severity of OCD symptoms was positively correlated with the severity of the trauma. This suggests that a genetic vulnerability only provides a partial explanation for OCD