Van der Sluis et al. (2012) recommended that researchers confirm positive findings of etiological moderation using the bivariate G × E model (see Fig. 1b; Purcell, 2002), since the extended univariate G × E model is unable to distinguish between moderation of the covariance path and moderation of the residual path (only the latter of which represents ‘true’ G × E). Although useful for confirming G × E in this way, the bivariate G × E model otherwise suffers from a number of problems, including issues of identifiability (Rathouz et al. 2008). Given these problems, we restricted our core G × E analyses to the extended univariate model, and made use of the bivariate model only to confirm those results.
