A family study of obsessive compulsive disorder

Background: We conducted a family study of obsessive-compulsive disorder to investigate subtypes and phenotypic spectrum of OCD. Methods: 80 case probands were identified in 5 OCD clinics, and 73 community control probands were identified by random digit dialing. These probands and their first-degree relatives (343 case and 300 control relatives) were evaluated by clinicians using semistructured instruments. Final diagnoses were assigned by a blinded-consensus procedure. Results: Lifetime prevalence of OCD was significantly greater in case than control relatives. Case relatives also had significantly greater prevalence of generalized anxiety disorder and agoraphobia, tics, pathological grooming behaviors, and obsessive-compulsive personality disorder, and they scored higher on neuroticism. Results from complex segregation analysis supported a Mendelian-dominant model with significant sex effects. The prevalence of OCD in relatives was strongly related to age at onset and compulsivity scores in female but not male probands. Conclusions: OCD is a familial disorder. Specific anxiety disorders, pathological grooming behaviors, tics, and personality disorders may be part of the familial spectrum. A Mendelian-dominant model best explains the inheritance of OCD in these families.