ABSTRACT
The causes of obsessive-compulsive disorder (OCD) are as yet unknown. Evidence of familial aggregation is one approach for investigating the role of genetics in the etiology of this condition. This chapter presents a family study to determine if OCD is familial and to investigate possible familial subtypes. The lifetime prevalence of OCD was significantly higher in case compared with control relatives. Case relatives had higher rates of both obsessions and compulsions; however, this finding is more robust for obsessions. The finding that OCD is familial is a necessary, albeit not sufficient, condition for genetic etiology. Clarification of the range of psychopathology that is transmitted in these families, as well as identification of etiologically homogeneous clinical subtypes, will increase the ability of association studies and genome-wide searches to detect genes involved in the pathogenesis of OCD.
