Since 1996, 33 states plus the District of Columbia have enacted medical marijuana laws allowing approved patients legal access to therapeutic cannabis. Additionally, since 2012, ten states and the District of Columbia have passed recreational marijuana laws legalizing adult use and?in eight states?retail sales. Although states continue to pass and amend these laws at a fast pace, little systematic evidence is available on the health, safety, and economic impacts of these laws. The handful of available reviews in this policy space focus mainly on the effects of medical marijuana laws on a narrow set of marijuana use outcomes. Policymakers therefore continue to enact, (re)design, and implement these laws with limited evidence-based guidance on their broader societal impacts. The primary aims of this work are twofold. First, we will develop a comprehensive evidence map of existing research examining the effects of medical and recreational marijuana laws on a diverse range of health, safety, and economic outcomes. This effort is designed to be broad in scope to fully document extant empirical research in this policy space. Second, we will quantitatively synthesize evidence from quasi- experimental studies examining the effects of medical marijuana laws on targeted public health and safety outcomes. This narrower delimitation is warranted because primary research on recreational marijuana laws and other outcomes remains nascent. Our analytic approach will employ random effects meta-regression models with robust variance estimation to account for dependent effect sizes coded from the same studies. This approach will further allow us to investigate important sources of heterogeneity in effect sizes across key study factors, including different target populations, time periods, and study designs. Lastly, we will communicate our findings using evidence-based strategies to increase knowledge utilization among the research and policy communities. Our work will contribute to improved policymaking on marijuana by producing systematic evidence- based knowledge, identifying ongoing policy uncertainties, and highlighting gaps and directions for future research.
There is pressing need to develop evidence-based knowledge on the public health and safety implications of marijuana liberalization laws. Current systematic reviews of the literature, however, are narrow in scope or qualitative in nature, limiting policymakers? ability to make informed policy decisions. The main goal of this research is to systematically map the empirical literature and perform a quantitative synthesis of quasi- experimental studies that investigate the effects of medical marijuana laws on public health and safety outcomes, and thereby produce evidence-based guidance to policymakers and highlight directions for future research.