However, genetically-informed studies indicate that environmental factors also play a significant role in the development of SUDs and AUDs (e.g., Caspi et al., 2005; Dick et al., 2007; Dick et al., 2007; Rose, Dick, Viken, & Kaprio, 2001). Many of these candidate environmental risk factors are more prevalent among COAs, and these factors likely underlie the broad-based emotional and behavioral impairments more evident in COAs than in their peers. By ages 2–3 and through young adulthood, COAs show greater internalizing and externalizing symptoms than do their peers (Hussong et al., 2007; Hussong, Flora, Curran, Chassin, & Zucker, 2008). COAs also show higher rates of problems in school (e.g., poorer academic performance; McGrath, Watson, & Chassin, 1999) and in their peer relationships (e.g., lower rates of social competence in childhood and greater risk of deviant peer affiliations in adolescence; Chassin, Curran, Hussong, & Colder, 1996; Hussong, Zucker, Wong, Fitzgerald, & Puttler, 2005). Most notably, COAs show a substantially greater risk for alcohol and drug use disorders in young adulthood. COAs initiate substance use earlier, increase their rates of use more quickly,
