Using twin models, we found statistically significant heritability and co-heritability of the TOCS total score and individual TOCS dimensions. However, power for detecting sex or age differences was limited. We showed that the genetic and environmental influences on the dimensions were best explained by an independent model and not by a latent trait. TOCS dimensions exhibited both shared and unique genetic influences. Hoarding was less phenotypically correlated with the other dimensions but was still genetically correlated and shared part of its additive genetic influences with other OC dimensions. Although Hoarding did standout phenotypically, it shared a common underlying etiology with other OC dimensions. Together our results show that the TOCS is an informative measure for genetic research when used either as a single global OC trait or as individual dimensions.
