Substance use disorders typically co-occur with each other (Stinson et al., 2005) and with other risk behaviors and mental health disorders (Kessler et al., 1997; Krueger, 1999; Regier et al., 1990). The association of childhood disruptive disorders and substance misuse is reflected in studies showing that attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD) are both comorbid with substance use disorders and forecast their development (Armstrong & Costello, 2002; Disney et al., 1999; Flory & Lynam, 2003; Kim-Cohen et al., 2003; Weinberg et al., 1998). These phenotypic associations have led several researchers to posit the existence of an underlying vulnerability to disinhibitory behavior, characterized in preadolescence by undersocialized behavior and low levels of dispositional constraint. Our own research supports the existence of this latent factor, which is highly heritable (Hicks et al., 2007; Krueger et al., 2002; Young et al., 2000) and transmitted from parent to child (Hicks et al., 2004). Moreover, this general factor accounts, in large measure, for the covariance across a broad range of indicators of externalizing psychopathology, including childhood disruptive disorders, substance abuse
