This model (Panel C of Figure 1) jointly tests the extent to which correlated and moderating influences shape the association between RSI and PSI (49). Drawing from the correlated influences hypothesis, the joint correlation-moderation model tests the extent to which overlapping and specific A, C and E factors influence liability to RSI. To incorporate moderation influences, both the overlapping and specific A,C and E influences on RSI are then moderated by PSI. For instance, the genetic influences on RSI can now be visualized as those overlapping with PSI (A21) and those specific to RSI (A22). Each of these genetic parameters are moderated by PSI such that the net genetic influences on RSI are (A21+X1*PSI) and (A22+X2*PSI). Here, both X1 and X2 support gene x environment interaction whereby the former represents G x E for additive genetic influences on RSI that are shared with PSI while the latter represents G x E for additive genetic influences specific to RSI.
