Interestingly, despite interest in the phenotypic (or observed) relationship between childhood disruptive behavior and alcohol use, very little work has focused on subtypes of ADHD (i.e., inattention and hyperactivity/impulsivity) or the underlying genetic and environmental structure of the interrelationships among ADHD, CD, and alcohol problems, particularly in adolescence. Specifically, an additional mechanism could account for apparent associations between externalizing behavior and alcohol use in adolescence such that these phenotypes may share common genetic variance (“common genes” hypothesis) whereby comorbidity may be best explained by genes with pleiotropic effects (i.e., genes that influence more than one trait). In support of this “common genes” hypothesis, the covariation between hyperactivity and CD (Silberg et al., 1996) and CD, ADHD, and Oppostional Defiant Disorder (Dick et al., 2005; Nadder et al., 2002; Waldman et al., 2001) in adolescence was found to be largely attributable to genetic factors, and there is fairly strong evidence that a common genetic factor underlies much of the phenotypic association among alcoholism, drug abuse, antisocial personality and CD in late adolescence and adulthood (Hicks et al., 2004; Krueger et al.,
