The multisite OCGAS comprised patients with OCD onset before the age of 18, recruited between 2007 and 2012 (Mattheisen et al. 2015). Study design and methods have been described previously (Samuels et al. 2006). A total of 1065 families were included; of these, 621 families were recruited and assessed specifically for this study at one of the five participating recruitment sites or the National Institute of Mental Health (NIMH), whereas 444 families had been evaluated previously in an earlier study at one of the collaborating sites. The complete sample comprised 460 trios (an affected proband and both parents), 155 pedigrees with a proband and an unaffected sibling, 450 families with another structure, and an additional 192 singleton probands.
