the variance in the target sample phenotype (Dudbridge, 2013; Wray et al., 2014). How much variance PRS explain is dependent upon the SNP heritability of the phenotype, the size of both the discovery GWAS and the target sample, the selection thresholds for SNPs included in the PRS, and the methods used for weighting the effect sizes (Dudbridge, 2013). The extent to which a PRS derived from a GWAS of alcohol consumption is associated with aspects of problem drinking is, therefore, an estimate of their genetic commonality, although causal processes can also be represented (Swerdlow et al., 2016).
