Cognitive aptitude, peers, and trajectories of marijuana use from adolescence through young adulthood

BACKGROUND: Using a nationally representative longitudinal cohort, we examine how cognitive aptitude in early adolescence is associated with heterogeneous pathways of marijuana use from age sixteen through young adulthood. We also examine whether this relationship can be explained by the role of cognitive aptitude in the social organization of peer group deviance. METHODS: Using the National Longitudinal Survey of Youth 1997, we identified 5 latent trajectories of frequency of marijuana use between ages 16 and 26: abstainers, dabblers, early heavy quitters, consistent users, and persistent heavy users. Multinomial regression assessed the relationship of cognitive aptitude in early adolescence with these latent trajectories, including the role of peer group substance use in this relationship. RESULTS: A one decile increase in cognitive aptitude in early adolescence is associated with greater relative risk of the dabbler trajectory (RR = 1.048; p < .001) and consistent user trajectory (RR = 1.126; p < .001), but lower relative risk of the early heavy quitter trajectory (RR = 0.917; p < .05) in comparison with the abstainer trajectory. There was no effect for the persistent heavy user trajectory. The inclusion of peer group substance use–either via illegal drugs or smoking–had no effect on these relationships. CONCLUSIONS: Adolescents who rate higher in cognitive aptitude during early adolescence may be more likely to enter into consistent but not extreme trajectories of marijuana use as they age into young adulthood. Cognition may not influence patterns of marijuana use over time via the organization of peer groups.