Genomic control lambda (λGC) revealed no significant evidence of population stratification in the male-specific (λGC=1.019), the female-specific (λGC=1.026), or the combined (λGC=1.051) meta-analyses. The intercepts estimated by LD score regression of 1.002, 0.991, 1.005 for sex-combined, female-only, and male-only, respectively, suggested that the mild inflation observed on the quantile-quantile plots (λGC) was not due to population stratification but rather to polygenic effects. The Manhattan and quantile-quantile plots (Figure 1 A-B) demonstrated no genome-wide significant associations in either males or females. There was little overlap in the top signals across sexes as illustrated by the lack of points along a diagonal line from the left bottom corner to the right upper corner of Figure 1C (top ten associations, Table 1). This visualization indicates that there are no variants which strongly associate (-log10(p-value)>3) with OCD in both sexes. In fact, the strongest associations in one sex, have very low -log10(p-value) in the opposite sex. Gene-based tests computed by MAGMA revealed two genome-wide significant genes in the female analysis: GRID2 (pFEMALE = 1.07E-07, pMALE = 7.23E-01) and GPR135 (pFEMALE = 1.55E-06, pMALE =
