Using data from two longitudinal studies, Fast Track and the Child Development Project, Jennifer Lansford, Research Professor in the Sanford School of Public Policy at Duke, Kenneth Dodge, William McDougall Distinguished Professor of Public Policy Studies at Duke, and colleagues examined how an individual’s attitudes toward peers and an individual's substance use develops from early adolescence to middle adulthood. This study found that peer selection may influence substance use more than influence and that perceptions of peers’ substance use in early adulthood predicted adults’ use in their fourth decade for cannabis, alcohol and opioids. Intervention efforts sometimes attempt to change norms about substance use by providing adolescents with information that their peers engage in less substance use or are less approving of substance use than individuals perceive them to be . An implication study findings for prevention efforts is that attempts to change individuals’ own use directly may be as effective as efforts to change individuals’ perceptions of peer norms.