In conclusion, we tested the robustness of three moderators previously associated with adolescent alcohol use. We assessed these effects using a systematic pipeline of GxE models, comprised of the bivariate twin model and the extended univariate model, to examine moderators that could potentially vary between twins. In addition, we tested if the effects were robust following two non-linear transformations of the alcohol use measure. We found that when the assumptions of the extended univariate model are met, the results generated do not differ from those of the corresponding bivariate moderation model. With regards to parental knowledge, the moderating effect showed the same pattern across the raw and transformed outcome variables. The effect was borderline significant after transformation indicating a more subtle relationship between parental monitoring and adolescent alcohol use. The moderating effect of potentially stressful life events on the genetic influences on alcohol use showed a trend in the raw variable and was significant using a transformed variable. Finally, along with having the strongest literature support, the effects of peer deviance were robust to both the model selection and transformation.
