As shown in Table 5 and as visually summarized in Figure S2, in the EA sample there was no evidence of interaction between parental relationship discord and offspring PRSALC on a multiplicative scale. However, the combined effect of parental relationship discord and PRSALC (i.e., OR = exp (0.21 + 0.27 + 0.04) = 1.68) was not equal to the sum of the individual effects, providing evidence of the presence of interaction on an additive scale (RERI = 1.68 − 1.23 − 1.31 + 1 = 0.14). A RERI of 0.14 indicates that for every unit increase in parental relationship discord and every unit increase in PRSALC, the relative risk of developing AUD is 0.14 more than if there were no interaction. In the AA sample, there was no evidence of interaction between parental relationship discord and offspring PRSALC on a multiplicative or additive scale.
