Impact of Medical Marijuana Laws on Marijuana Use by Young People

"In summary, current evidence does not support the hypothesis that MML passage is associated with increased marijuana use prevalence among adolescents in states that have passed such laws up until 2014. Based on this evidence, we recommend several steps to advance the understanding of current and future marijuana policy effects. First, continued exploration of the effects of these state policies on different measures of use among adolescents is warranted. While evidence is clear regarding MML effects on annual and past-month prevalence, evidence regarding effects on daily/near-daily use, marijuana abuse/dependence and intensity of use have not been explored as thoroughly, and warrant additional consideration in light of decreasing national trends in marijuana risk perceptions among adolescents [54,86]. Secondly, continued monitoring of adolescent marijuana use in MML states is critical in light of differential development of commercialized markets. Recent studies have shown a rapid diffusion of medical marijuana stores and increased commercialization in selective states following the 2009 Ogden memo,which de-prioritized federal enforcement against individuals compliant with state MMLs [51,75,87–89]. Studies evaluating the impact of this rapid commercialization on youth marijuana use have shown a more consistently positive effect [51,90,91]. Such findings are particularly relevant in light of recent recreational marijuana laws, all of which so far allow commercial distribution systems [92]. Thirdly, further studies should be conducted in adults, for which the limited literature suggests a positive effect of MMLs on marijuana use [65,69,75]. Fourthly, investigators should experiment with process-based models of information and product diffusion that can estimate MML effects even in the presence of spill-over effects into non-MML states [93]. Finally, increased coordination among researchers across multiple disciplines is needed to maximize efficiency in studying these urgent research questions in the context of rapidly changing marijuana policy."