One strategy for improving the power of genetic studies in OCD is to focus on OC traits rather than on OCD diagnoses and to measure these traits in a way that generates widely distributed scores in the general population. The added variance and scope of behaviors captured by these trait-based measures may improve power and reduce error in genetic studies. We developed the TOCS to measure the full range of OC traits in youth21. To be informative for genetic research of OCD, the TOCS should be heritable and so should any OC trait dimensions that it captures. The TOCS factored into six heritable and co-heritable OC dimensions similar to those reported from studies using existing OCD scales13,14. We used ACE twin models to compare independent and common pathway models and to assess the degree to which dimensions shared etiological factors. 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
