sample size, another approach to improve power for GWAS is to reduce genetic heterogeneity. For example, if sex significantly modifies the effect of genetic variation on the risk of OCD, then combining males and females with OCD may weaken or obscure sex-specific effects. For example, previous studies have discovered novel loci which were previously undetected due to heterogeneity between sexes (Mitra et al. 2016; Martin, Walters, Demontis, Mattheisen, Hong Lee, et al. 2017; Taylor et al. 2013; Randall et al. 2013; Liu et al. 2012; Winkler et al. 2015; Hartiala et al. 2016; Orozco et al. 2012; Zhuang and Morris 2009; Singh et al. 2016). Motivated by the sex differences in OCD, we tested the hypothesis that the genetic architecture of OCD varies between the sexes.
