All of the remaining studies of families ascertained through adult individuals with OCD provide evidence that OCD is a familial disorder.38,53,55-58,60 In these studies, the rate of OCD among relatives of affected individuals was significantly higher than either the estimated population prevalence or rate among controls. In the most recently published study,60 the investigators ascertained affected individuals from both a population sample and a clinic sample. They observed a significant increase in both relatives of individuals who were ascertained through an OCD clinic and individuals who were identified through a population study of OCD. The study by Grabe et al was the first controlled study of OCD in Europe, and confirmed the results of earlier studies completed in the US38,56,58 with families ascertained through treatment facilities. The finding that relatives of both clinic patients and individuals identified in a population based study is important. As the authors nicely summarize, “the finding of a comparable familial aggregation of definite OCD and a higher familial aggregation of subclinical OCD in relatives of never treated persons with OCD from the community strongly supports the impact of familial-genetic factors in OCD.”
