A systematic review and meta-analysis published this month in the Journal of the American Academy of Child and Adolescent Psychiatry found that the legalization of recreational marijuana is associated with increases in past-month marijuana use among adolescents and young adults. As opposed to lifetime or past-year use, past-month use is indicative of more frequent use. The study’s co-authors are affiliated with the Johns Hopkins School of Medicine and Harvard Medical School.
Notably, the meta-analysis found that recreational marijuana laws were associated with a 13% increase in past-month marijuana use among youth, defined as those between the ages of 12 and 17. Likewise, among studies with datasets only after 2008, it found that recreational marijuana laws were associated with a 22% increase in past-month marijuana use among young adults, defined as those between the ages of 18 and 25. These results were statistically significant.
The study noted, “the fact that analyses accounting only for more recent trends (ie, studies using data after 2008) showed a significant increase in cannabis use among adolescents is alarming,” recognizing that “neurodevelopment from adolescence continues into the early 20s and may be disrupted by chronic cannabis use.” It added that “small changes in the prevalence of cannabis use can have large impacts on public health outcomes for this population.”
The strength of a systematic review is that it synthesizes existing studies, thus reducing the possibility of bias from any one observed outcome. This review also focused on studies that used the difference-in-difference technique, which accounts for relative trends between the treatment and control groups over time.
Echoing SAM’s positions, the study argued that legislators “must ensure that laws promoting legalization strongly consider the potential adverse public health outcomes over the benefits from permissiveness toward commercialization of cannabis, and strengthen the cannabis use prevention and treatment efforts for youth to mitigate the risk of adverse health consequences.”