Moderated multiple regression analyses indicated that parental knowledge and peer deviance moderated the associations of polygenic scores with age 14 alcohol problems (Table 3). Genetic influences were more pronounced under conditions of low parental knowledge or high peer deviance compared to conditions of high parental knowledge or high peer deviance (Figure 2). The interactions with parental knowledge and peer deviance accounted for 0.33% and 0.30% of the variance in alcohol problems, respectively. To verify that our effects were not driven by non-independence within the sample, we note that the same pattern of effects was found when we re-ran the moderation analyses after randomly dropping one member from each twin pair (n = 634).
