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 in contrast to the majority of studies showing that males have greater hyperactive–inattentive symptoms than females [68]. However, female gender predicts the unique variance in hyperactive–inattentive symptoms after partialling out impulsivity and sensation seeking, possibly explaining the unusual direction of risk. In post hoc analyses that removed impulsivity and sensation seeking (but not other predictors) from the model, gender no longer significantly predicted hyperactive–inattentive symptoms (β = −0.08, ns).
