As shown in Table 3, 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., HR = exp (0.07 + 0.13 + 0.02) = 1.25) was not equal to the sum of the individual effects, providing evidence of the presence of interaction on an additive scale (RERI = 1.25 − 1.08 − 1.14 + 1 = 0.03). A RERI of 0.03 indicates the increased hazard due to additive interaction. In the AA sample, there was no evidence of interaction between parental relationship discord and offspring PRSALC on a multiplicative or additive scale.
