Genetic and environmental influences on obsessive-compulsive symptoms in adults: a population-based twin-family study

Abstract

BACKGROUND: The contribution of genetic factors to obsessive-compulsive (OC) symptoms has not been examined using a large population-based sample of adults. Furthermore, the extent to which there are qualitative and quantitative differences in genetic architecture between men and women with OC symptoms has not been elucidated. METHOD: We obtained the Young Adult Self Report Obsessive-Compulsive Scale (YASR-OCS) from a group of 5893 monozygotic (MZ) and dizygotic (DZ) twins, and 1304 additional siblings from the population-based Netherlands Twin Register. Structural equation modelling was used to decompose the variation in OC behaviour into genetic and environmental components and analyse quantitative and qualitative sex differences. RESULTS: Familial resemblance was the same for DZ twins and non-twin siblings, which means that there was no evidence for a special twin environment. The same genetic risk factors for OC behaviour were expressed in men and women. Depending on the choice of fit index, we found small (39% for men and 50% for women) or no sex differences (47% for both men and women) in heritability. The remaining variance in liability was due to individual-specific environment. CONCLUSIONS: OC behaviour showed a moderate heritability. At most, small quantitative sex differences were found in the genetic architecture of OC behaviour, and no qualitative sex differences.