A family genetic study of clinical subtypes of obsessive-compulsive disorder

Objective The results of various family studies of obsessive-compulsive disorder have varied widely, possibly because of heterogeneity in the obsessive-compulsive disorder phenotype. The current study was conducted to determine familiality of checker and washer subtypes of obsessive-compulsive disorder compared with normal controls. Methods In this study, all available first-degree relatives of 25 checker, 34 washer and 40 psychiatrically normal control probands were interviewed directly, using structured interviews. Results The morbid risk of syndromal and subsyndromal obsessive-compulsive disorder was significantly greater among the relatives of checker probands (119.4%) than in the relatives of washer (8.7%) or control probands (5.4%), while the morbid risk for the relatives of washer and control probands was not significantly different. In all, 67% of the checker relatives with syndromal and subsyndromal obsessive-compulsive disorder were checkers, while 54% of the washer relatives with syndromal and subsyndromal obsessive-compulsive disorder were washers. Conclusions Our study provides preliminary evidence of familiality of the checker subtype of obsessive-compulsive disorder. Future studies using patients subtyped on the basis of symptom dimensions, in larger obsessive-compulsive disorder samples, are needed, to further validate the genetic basis of obsessive-compulsive disorder.