Trajectories of marijuana use from late childhood to late adolescence: Can Temperament × Experience interactions discriminate different trajectories of marijuana use?

Informed by developmental ecological and epigenetic theory, the current study examined three aims concerning adolescent marijuana use with a large community sample (N = 755; gender = 53% female) and six annual assessments that spanned 11-18 years of age. First, the natural history of adolescent marijuana use was modeled using a two-part latent growth curve analysis. Second, the validity of the mixtures was examined with a broad array of known correlates of adolescent marijuana use. Third, temperament (e.g., surgency, effortful control, and negative affect) was tested as individual differences that would enter into statistical interactions with peer substance use and prior alcohol and cigarette use to distinguish trajectories of marijuana use. The results suggested that escalations in marijuana use were observed for some youth who initiated marijuana use early in adolescence. Youth whose marijuana use did escalate substantially (10%) were distinguished on temperament, conduct disorder, peer delinquency, and pubertal development at baseline. Furthermore, hypothesized interactions between surgency and both peer substance use and prior substance use discriminated different patterns of marijuana use. The findings are discussed with respect to strategies for timing and content of preventive interventions.