The present study sought to predict early-adulthood substance abuse and dependence (tobacco, alcohol, and marijuana) from adolescent substance use, friends’ support for use, the direct and interaction effects of the construct of effortful control. The major hypotheses of our study were that (a) high levels of adolescent effortful control will predict reduced problematic substance use in early adulthood, (b) adolescent friends’ support of substance use will predict growth in problematic substance in early adulthood, and (c) high levels of adolescent effortful control will play a moderator role by promoting resiliency to the risk factors of a history of adolescent substance use and friends’ support of substance use.
