This study has a number of strengths. First, we used a genetically-informative design to understand the mechanisms through which genetic risk unfolds to influence alcohol use. Notably, our results showed that alcohol consumption polygenic scores remained significantly associated with phenotypic alcohol use, above and beyond the effects of important covariates (e.g., age, sex), sensation seeking, and social support from family and friends. This highlights the robustness of genetic effects and the need to examine other biological and psychosocial mechanisms underlying genetic risk for alcohol use outcomes. Second, we conducted simultaneous tests of sensation seeking and social support as indirect pathways to delineate the pathways by which genetic influences impact alcohol use. Considering multiple mediating pathways simultaneously allowed for examination of the unique effects of each specific pathway. In addition, we considered alternative conceptual models to examine both rGE and GxE, which allows for a more comprehensive examination of the varying roles that social support could play in the relation between alc-GPS and alcohol use. We also considered social support from family and friends, allowing us to understand whether pathways of
