We created polygenic scores derived from a large-scale GWAS of number of alcoholic drinks per week in approximately 1 million individuals [15]. As FinnTwin12 was included in the original discovery GWAS, we obtained summary statistics with all Finnish participants, including FinnTwin12 and 23andMe (which are not publicly available) cohorts removed (available n = 534 683). There were 3 707 235 autosomal SNPs in common after quality control. We used the well-established process of clumping and thresholding [51]. SNPs from the discovery GWAS were clumped based on linkage disequilibrium (LD) using the clump procedure in PLINK [52], based on an R2 = 0.25, with a 500 kb window, resulting in 407 604 independent SNPs for creating scores. We then created scores based on differing thresholds of GWAS P-values (P < 0.0001, P < 0.001, P < 0.01, P < 0.05, P < 0.10, P < 0.20, P < 0.30, P < 0.40, P < 0.50). We converted GPS to Z-scores for interpretation.
