Interestingly, GABRA2 did not have direct effects on hyperactive–inattentive symptoms or conduct problems in the final model, nor did GABRA2 have significant zero-order correlations with alcohol problems, hyperactive–inattentive symptoms, or conduct problems. On the other hand, GABRA2 variation directly predicted the latent factors of impulsivity and sensation seeking in the final model and demonstrated several zero-order correlations with manifest impulsivity and sensation seeking variables. Because GABRA2 variation was more consistently associated with disinhibition than with externalizing symptoms, this suggests that it is more strongly related to the personality-related underpinnings of externalizing problems than with the symptoms themselves (which are likely more heterogeneous). This is in line with a recent meta-analysis that showed larger genetic effects on trait compared to diagnostic phenotypes [31]. Results demonstrate the utility of including phenotypes that might be more proximal to genetic influences to elucidate the influence of genes on clinical outcomes [72]. It is possible that non-replications in the literature might be due to the failure to consider possible intermediate phenotypes. Of note, in the final model females had greater adolescent hyperactive–inattentive symptoms. This stands
