Genetic risk for alcohol problems was indexed using genome-wide polygenic scores (PRS), which are an aggregate measure of the number of risk alleles individuals carry, weighted by effect sizes from GWAS summary statistics (Wray et al., 2014). We calculated PRS using PRS-CS “auto” (Ge et al., 2019), which employs a Bayesian regression and continuous shrinkage method to correct for the non-independence among nearby SNPs in the genome (i.e., linkage disequilibrium, or LD). We derived the alcohol problems PRS using meta-analyzed GWAS weights (detailed in Barr et al., 2020) from the EA subset of the Psychiatric Genomic Consortium’s (PGC) GWAS of alcohol dependence (Walters et al., 2018) and a GWAS of the problem subscale from the Alcohol Use Disorders Identification Test (AUDIT-P) in UK Biobank’s (Sanchez-Roige et al., 2019). Higher polygenic scores indicated higher polygenic liability for alcohol problems.
