The SNP heritability of our GWASs was lower than that seen in the meta-analysis of the UKBB and 23andMe data8. For the AUDIT-C, the estimated SNP heritability was 0.068 in EAs (0.068 in males and 0.099 in females) and 0.062 in AAs. For AUD, the estimated SNP heritability was 0.056 in EAs (0.054 in males and 0.110 in females) and 0.100 in AAs. These estimates may reflect the lower number of SNPs tested in our sample compared with the meta-analysis of UKBB and 23andMe data. The nominally higher SNP heritability in females than males could be due to the substantially smaller size of the female subsample. Alternatively, women could have a higher liability-threshold and therefore a higher burden of risk variants. Because our study sample was predominantly male, we do not have adequate statistical power to evaluate these hypotheses. Although we found no significant difference in PRS between males and females, because of the substantially smaller number of women in MVP, there is much less power for the PRS in this subgroup and for comparing the PRS by sex.
