Obsessive-compulsive disorder is one of many neuropsychiatric traits exhibiting sex differences in both age of onset and presentation of symptoms. Gene-based analysis identified two genes (GRID2 and GPR135) with female-specific associations that were not present in males, however, at the level of individual loci, no genome-wide significant associations were detected in either the sex-stratified GWAS or the genotype-sex interaction analysis. The genome-wide genetic correlation for OCD between males and females was not significantly different from 1 and OCD heritability estimates were not significantly different between the sexes. Additionally, we observed no significant differences in the cross-trait genetic correlations between males and females which is currently best explained by the absence of ubiquitous genetic architecture differences between male and female OCD, as well as small sample sizes which negatively impact on the ability to detect smaller differences between the sexes. Finally, partitioned heritability analysis indicated that the X chromosome contributed to the polygenic liability of OCD, underscoring the importance of including the X chromosome in GWAS of OCD.
