When examining the risk of any AD in relatives of index persons with OCD, compared to relatives of persons who did not have OCD, we found that the association was strongest and statistically significant among first-degree relatives (Table 2). Mothers, fathers, and full siblings of individuals with OCD were each significantly more likely to be affected with an AD. The risk was marginally higher among mothers (17% increase) and siblings (16% increase) than among fathers (8% increase), but CI overlapped. The associations between OCD and AD in second-degree relatives (maternal or paternal half siblings) or in cousins were lower than for first-degree relatives and none were statistically significant (Table 2). Family-level analyses of individual AD followed the same general pattern (Supplementary Table 2).
