Antecedents and outcomes of marijuana use initiation during adolescence

Background. This study identified similarities and differences in risk factors for marijuana use initiation from grades 7 to 8, grades 8 to 9, and grades 9 to 10, and examined differences between earlier initiates, later initiates, and nonusers on various problem behaviors at grade 10. Method. Longitudinal data were used to examine predictors and outcomes associated with marijuana initiation from grade 7 (N = 1,955) to grade 10 (N = 909). Participants completed yearly surveys to assess problem behaviors, social influences, and marijuana-related attitudes and behavior. Results. Earlier initiates were more likely than later initiates to exhibit problem-related marijuana use, hard drug use, polydrug use, poor grades, and low academic intentions at grade 10. Across ages, initiation was predicted by smoking, frequency of marijuana offers, and poor grades. Results provided some evidence for a shift from familial to peer influence on marijuana initiation with increasing age. Marijuana-related beliefs were relatively weak predictors of initiation at all ages after controlling for pro-marijuana social influences and engagement in other types of substance use and delinquent behavior. Conclusions. Results emphasize the importance of early intervention and identify a wide range of potentially modifiable risk factors that may be targeted.