Given this high likelihood of etiologic heterogeneity, it is critical to study a sufficiently large sample of affected individuals so that homogeneous clinical subgroups more likely to be etiologically homogenous can be identified from within the larger sample.140-141 In order to obtain these large samples, it is imperative that investigators interested in the genetics of OCD collaborate. A collaboration of this type (the International OCD Foundation Genetics Collaborative) is currently conducting a GWAS of OCD on samples contributed from 21 different research sites from around the world.
