Five findings are noteworthy. First, alcohol consumption PRS predicted a very modest proportion of variance (< 0.6%) in DSM IV alcohol dependence (DSM4AD) and DSM 5 AUD symptomatology (DSM5AUDSX). This estimate is relatively consistent with the extent to which PRS tend to explain cross-trait variance. For instance, a recent study examined the extent to which alcohol consumption PRS (derived from a smaller meta-analysis; Schumann et al., 2016) predicted recent drinking (alcohol consumption and AUDIT scores) in a sample of 5,456 participants aged 18–83 years (Mies et al., 2018); at the most predictive thresholds, alcohol consumption PRS predicted 0.11% of the variance in recent drinking. A similar analysis of the Avon Longitudinal Study of Parents and Children (ALSPAC) found that an 89-SNP risk score (derived from literature searches) predicted up to 0.66% of the variance in typical alcohol consumption (Taylor et al., 2016). Despite this consistency, the AUC estimate suggests that the consumption PRS minimally (but significantly) improves classification for DSM4AD. These findings point to the extremely high polygenicity underlying alcohol intake and problem drinking such that even the aggregated effects
