As shown in Table 3, in the EA sample, there was no evidence of interaction between exposure to parental divorce and offspring PRSALC on a multiplicative. However, the combined effect of parental divorce and PRSALC (i.e., HR = exp (0.30 + 0.14 + 0.01) = 1.57) was not equal to the sum of the individual effects, providing evidence of the presence of interaction on an additive scale (RERI = 1.57 − 1.35 − 1.15 + 1 = 0.07). A RERI of 0.07 indicates the increased hazard due to additive interaction. In the AA sample, there was no evidence of interaction between parental divorce and PRSALC on a multiplicative or additive scale.
