Obsessive-compulsive disorder (OCD) is characterized by recurrent and intrusive thoughts and ritualistic behaviors or mental acts that a person feels compelled to perform. Although the etiology of OCD remains unknown, the results of twin studies, familial studies, and segregation analyses have provided compelling evidence that OCD has a strong genetic component [1]. However, OCD fails to follow Mendelian patterns of inheritance and is considered a complex genetic disorder. Several theoretically relevant functional candidate genes have been examined in OCD, but no susceptibility genes have yet been identified with certainty [1]. Like in other neuropsychiatric conditions, the difficulty in identifying the responsible genes may be the consequence of the clinical and genetic heterogeneity of the disorder.
