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 have twin studies shown on the biological explanation for OCD?
Nestaat (2010)
Reviewed twin studies and that found that 68% of MZ twins shared OCD compared to 31% of DZ twins.
This can help us assume that OCD is geneticallybased because the degree of concordance is significantlyhigher (and almost double) in MZ than DZ twins.
What are candidate genes and what do they show about OCD?
Genes found to be moreprevalent in OCD people.
OCD is found to be polygenic: up to 230 genes may be involved in OCD.
