Abstract
This study predicts that heterogeneous smoking trajectories covering four time points pose differential risks for dependence on alcohol and illegal drugs in young adulthood in an African American and Puerto Rican community sample (N = 475). The trajectory analysis yielded four smoking groups: nonsmokers, maturing out smokers, late-starting smokers, and early-starting continuous smokers. The early starting continuous group was more likely to become both alcohol- and drug-dependent in young adulthood than the other groups. Late-starting smokers were at higher risk than nonsmokers for drug dependence. Interventions are necessary from preadolescence through late adolescence to reduce the numbers of early and late smokers and their specific risks for substance dependence.