Second, we ran a set of set of analyses to examine whether our pattern of results was robust when controlling for divorce and separation status, college attendance, gene-by-covariate and covariate-by-environment interactions, and family ascertainment status. Prior research suggests that divorce and separation are associated with greater alcohol problems (Grant et al., 2015; Kessler et al., 1998) and that college students are more likely to engage in heavy episodic drinking than their non-college peers (Johnston et al., 2015; O’Malley & Johnston, 2002; Slutske, 2005). We observed the same pattern of effects after removing divorced and separated individuals from the unmarried group as was observed in the primary polygenic risk score analyses, allowing us to rule out the possibility that our observed effects were due to the inclusion of this subgroup. Likewise, we observed the same pattern of effects when controlling for college attendance, suggesting that our findings were not driven by individuals’ college student status. Next, we reran our analyses controlling for gene-by-covariate and covariate-by-environment interactions to address any concerns that our gene-by-environment effects were confounded (Keller, 2014). When controlling for
