Two approaches have been used to investigate sex differences in GWAS: (a) estimation of heritability using either genomic relatedness matrix restricted maximum likelihood (GREML), or linkage disequilibrium score regression, (LDSC) and (b) calculation of sex‐specific PRS, an average of risk alleles across the genome weighted by effect size and statistical significance. 121 Hall and colleagues 116 conducted sex stratified analyses in the UK Biobank and the Generation Scotland studies, and found similar SNP‐based heritability for depression in males (h 2 SNP = 0.18, SE = 0.06) and females (h 2 SNP = 0.22, SE = 0.06), whereas Duncan and colleagues 118 report substantially higher SNP‐based heritability for PTSD in females (h 2 SNP = 0.21, SE = 0.09) than in males (h 2 SNP = 0.08, SE = 0.10). The depression study also describes the balance between modeling sources of heterogeneity including sex differences and disease subtypes in the overall sample, and the loss of power in stratified analyses that use only a portion of the sample. Likewise, Martin and colleagues 95 hypothesized that under a liability threshold model, females
