Our findings have important practical implications for researchers and clinicians interested in those at greater risk for alcohol misuse. First, the signal for genetic associations may be drastically reduced in young adults in a committed relationship. Future research on gene identification efforts may benefit from the inclusion of important environmental information in order to increase power to detect genetic variants associated with various forms of alcohol misuse. Considering that G × E in the discovery GWAS may be of even more importance with regard to alcohol use phenotypes, as there is consistent evidence of G × E from twin studies [9,34,60,61]. For clinicians, these analyses point to committed relationships as a malleable environmental condition that may help reduce individuals’ level of misuse, in part, by limiting realization of genetic predisposition. Gene–environment correlation (rGE, or when exposure to an environment is influenced by one’s genotype) is always an important consideration, as the presence of rGE can give rise to spurious evidence of G × E [41]. We note that our GPS was uncorrelated with relationship status, increasing the likelihood that the evidence for G × E in the current sample is not due to rGE.
