became stronger as alcohol availability increased (Fig. 1 , left panel). The average marginal effect of FH in only extended family members (compared to negative FH) was associated with increases in high-risk drinking at low levels of alcohol availability (Fig. 1, right panel), but this FH effect became non-significant as alcohol availability increased to 10+ outlets per square mile. However, the interaction of alcohol availability with only extended family was not significant (F(1,18952) = 0.12, p = .73). Predicted probabilities of high-risk drinking are shown in Fig. 2 for selected levels of alcohol availability, with higher values representing more urban settings. Testing the simple slope for alcohol availability across the four levels of FH revealed that alcohol availability was only significantly associated with high-risk drinking for people with either an affected first-degree relative (average marginal effect = 0.013, p = .034) or both a first-degree relative and extended family with alcohol problems (average marginal effect = 0.019, p = .016).
