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 geneticfactor 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 geneticbasis because the degree of concordance is significantlyhigher in MZ twins than DZ twins
What is a limitation for the genetic explanation of OCD?
Environmentalrisk factors: Cromer (2007) found overhalf of people with OCD had experienced past trauma, and the severity of OCD symptoms was positivelycorrelated with the severity of the trauma. This suggests that a geneticvulnerability only provides a partialexplanation for OCD
