Next, we examined whether the ACE effects on the EXT composite changed as a function of the environmental context, operationalized as different levels of the environmental risk factors. This G-E interplay model (depicted in Figure 1) can be conceptualized as a bivariate extension of the univariate mode that incorporates additional moderation terms on the ACE effects39. The first part of this G-E interplay model estimates the ACE contributions to the covariance between EXT and the environmental risk factor (e.g., the genetic covariance is a11× a21), as well as the ACE effects that are unique to EXT (e.g., a22). This allows for the estimation of the G-E correlation between EXT and the environmental variable, which accounts for any selection effects between EXT and exposure to the environmental risk factor.
