In summarizing the studies published prior to 2006, van Grootheest and colleagues6 concluded that “in children, obsessive-compulsive (OC) symptoms are heritable, with genetic influences in the range of 45% to 65%. In adults, studies are suggestive for a genetic influence on OC symptoms, ranging from 27% to 47%...” The findings from the two most recent studies29,30 are remarkably similar when cotwins who met criteria for subclinical OCD were included in the analyses. Both studies reported that additive genetic effects accounted for 29% of the variance for OCD and subclinical OCD. In the Bolten study,29 familial aggregation due to combined additive genetic and shared environmental effects accounted for 47% of the phenotypic variance. Unfortunately, these investigators were unable to estimate the effects of additive genetic and shared environmental separately.29
