In the present study, we systematically re-examined GxE effects for three environmental factors—peer deviance, parental knowledge, and potentially stressful life events—that have been widely studied in the adolescent alcohol use literature and have been shown to moderate latent or measured genetic influences on adolescent externalizing behavior. Peer deviance, parental knowledge and stressful life events can differ between twins and therefore have the potential to correlate with the co-twin’s trait leading to the detection of false positive GxE interactions. Following the recommendations of van der Sluis et al. (2012), we examined GxE for these environmental factors and adolescent alcohol use in the bivariate and extended univariate models (when relevant). In addition, we ran a series of analyses examining whether our results were robust to non-linear transformations of the alcohol use outcome.
