Based on this literature, the major aim of the current study was to examine associations between GABRA2 and adolescent externalizing problems and to test whether impulsivity and/or sensation seeking mediated these relations. These associations were tested in a longitudinal high-risk sample, in which approximately half of the adolescents had parents with substance use disorders. Impulsivity, sensation seeking, baseline conduct problems, alcohol problems, and hyperactive–inattentive symptoms were measured 18 months prior to the outcomes of conduct problems, alcohol problems, and hyperactive–inattentive symptoms. We first tested proposed mediational models without controlling for baseline externalizing problems to simply evaluate associations between the constructs. Next, we tested these models while controlling for baseline externalizing problems to establish the directionality of the relation between impulsivity/sensation seeking and externalizing problems and to test whether GABRA2 predicts change in these externalizing problems over 18 months. Both these models were tested for several reasons. First, because stability in problem behaviors might be more genetically influenced [44] while change in symptoms over time might be more environmentally influenced [45], we wanted to ensure that we were not weakening genetic
