Here, we test this hypothesis using molecular genetic data in a population-based sample of young adults [36]. We focused on young adulthood because it is a critical period for the development of alcohol use patterns and problems [34], with heavy alcohol use at its highest point [37] and the peak age of onset for alcohol related disorders falling during this period [38]. Young adulthood is also a period when romantic partnerships become increasing salient, as young adults in committed relationships consume less alcohol than their single peers [39]. We used results from the largest mega-analysis to date on alcohol consumption [15], which used drinks per week in ~1 million individuals, to calculate genome-wide polygenic scores in our independent, population-based sample. We tested: (1) whether these polygenic risk scores were associated with alcohol use, heavy consumption and alcohol problems; (2) whether being in a romantic relationship changed the association between genetic risk and alcohol outcomes; and (3) because there are sex differences in patterns of alcohol use and in the prevalence of alcohol use disorders [38] and heavy consumption [37] and
