The role of genetics in the etiology of obsessive–compulsive disorder (OCD) is well established1. OCD is familial and heritable2–5. In children and adolescents, genetic effects account for most of the variance (heritability estimates of 45–65%)6 and the stability of symptoms across development7, with common environment only playing a role in early adolescence8,9. However, there are few replicated genetic risk variants for OCD. Gene discovery has been hampered by relatively small samples, which international consortia are working to overcome10.
