We observed 7.8% SNP-based heritability (p = 1.01×10−40) calculated on the basis of the summary association data in “G1” EUR via LD score regression (LDSC). As with other large-scale GWAS(25), an inflated lambdagc value was observed in the summary association data (λgc=1.16; Supplementary Figure 2). The LDSC intercept was 1.011 (SE = 0.0091), however, demonstrating that this inflation was due to polygenicity and not to population stratification, phenotype distribution, or other confounders. (25). In the smaller AFR sample (n=17,029), no effect of polygenicity was observed in the summary association data (λgc=1.01; Supplementary Figure 3). Four independent GWS regions were identified in “G1” EUR (Figure 1). The lead region was on chromosome 4, lead SNP rs1229984 (p=4.9×10−47; Figure 2a); gene ADH1B, (beta subunit, class I alcohol dehydrogenase). GWS SNPs mapped to numerous loci in the region, so we performed conditional analysis for these loci using GCTA with EUR summary statistics and 1000G data as reference LD. This analysis confirmed that there are only four independent signals, i.e. no associated region reflected more than one independent signal. The other three associated regions
