(Figure 2; Supplementary Table 9). Reassuringly, we identified 3.6 times more EXT loci than QSNP loci (579/160). Using a less stringent significance threshold by focusing specifically on the 579 EXT loci, only 7% (41/579) were significant for QSNP (one-sided QSNP P < 0.05/579). The observation that a small minority of the EXT loci were heterogeneous at either significance threshold, and that the vast majority of the 160 QSNP loci were found outside of EXT loci, provide evidence that the EXT loci primarily index a unitary dimension of genetic liability rather than representing an amalgamation of variants with divergent associations across the discovery phenotypes. Notably, the strongest QSNP and most salient example of a heterogeneous, trait-specific association is SNP rs1229984 (one-sided QSNP P = 1.67×10−51; Supplementary Data 1A). This particular SNP, located in the gene ADH1B, is a missense variant with a well-established role in alcohol metabolism25, and it was not associated with EXT (two-sided P = 0.022) but only with problematic alcohol use (two-sided P = 6.43×10−57). Additionally, for each of the 579 EXT SNPs, we investigated the concordance in direction of SNP effects (i.e., the sign) on the seven phenotypes (Supplementary Information section 3.5.4). For 317 of the 579
