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Perceived Friends’ Use as a Risk Factor for Marijuana Use Across Young Adulthood

Marijuana use is increasingly common among teens and young adults, but the prevalence and risk factors may vary throughout an individual’s young adulthood.  One factor that often predicts adolescent and college student marijuana use is the presence of marijuana-using peers and perceived social norms. This study was conducted to evaluate this relationship at different ages, which may inform age-appropriate interventions. The study examines how the associations between perceived friends’ marijuana use and own marijuana use change from age 18 to 30 using longitudinal data from a study that has been ongoing since 1976 (the Monitoring the Future study). Participants were enrolled and surveyed during their senior year of high school and completed follow-up surveys biennially. Variables collected include demographics, marijuana use, and perceived friends’ use of marijuana. The prevalence of marijuana use was stable from ages 18 to 20 and declined more rapidly after age 21. Perceived friends’ use was an average of 2.5 friends and decreased to 2. This study found a significant, positive, and increasing effect of perceived friends’ use on marijuana use across ages through age 30, with an increase in odds of past 12-month use associated with a one-unit increase in perceived friends’ use. The effect of perceived friends’ use on odds of marijuana use was significantly stronger for males compared with females from ages 19 to 24 and ages 27 to 30. Blacks, Hispanics, Other races had significantly lower odds of marijuana use than Whites across all ages. Participants with parents that have at least some college education had significantly higher odds of marijuana use compared to those with less educated parents.

Take away: The findings of this study indicate that the association between perceived friends’ marijuana use and an individual’s own use of marijuana strengthens with age and is strongest around age 28.  These findings suggest that peer selection and peer influence are persistent factors of substance use into an individual’s late twenties. Intervention strategies that acknowledge the roles of peers and their effect on substance use are needed beyond alcohol initiation and adolescence.


Patrick, M. E., Kloska, D. D., Vasilenko, S. A., & Lanza, S. T. (2016, October 13). Perceived Friends’ Use as a Risk Factor for Marijuana Use Across Young Adulthood. Psychology of Addictive Behaviors. Advance online publication.

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