Early evidence of the impact of cannabis legalization on cannabis use, cannabis use disorder, and the use of other substances: Findings from state policy evaluations

Abstract

Background: The past decade has seen unprecedented shifts in the cannabis policy environment, and the public health impacts of these changes will hinge on how they affect patterns of cannabis use and the use and harms associated with other substances. Objectives: To review existing research on how state cannabis policy impacts substance use, emphasizing studies using methods for causal inference and highlighting gaps in our understanding of policy impacts on evolving cannabis markets. Methods: Narrative review of quasi-experimental studies for how medical cannabis laws (MCLs) and recreational cannabis laws (RCLs) affect cannabis use and use disorders, as well as the use of or harms from alcohol, opioids, and tobacco. Results: Research suggests MCLs increase adult but not adolescent cannabis use, and provisions of the laws associated with less regulated supply may increase adult cannabis use disorders. These laws may reduce some opioid-related harms, while their impacts on alcohol and tobacco use remain uncertain. Research on RCLs is just emerging, but findings suggest little impact on the prevalence of adolescent cannabis use, potential increases in college student use, and unknown effects on other substance use. Conclusions: Research on how MCLs influence cannabis use has advanced our understanding of the importance of heterogeneity in policies, populations, and market dynamics, but studies of how MCLs relate to other substance use often ignore these factors. Understanding effects of cannabis laws requires greater attention to differences in short-versus long-term effects of the laws, nuances of policies and patterns of consumption, and careful consideration of appropriate control groups.

Cannabis legalization: progress in harm reduction approaches for substance use and misuse

“…In contrast to the findings in adolescents, the reviews by Smart and Pacula (38) and Hasin et al (39) both conclude that cannabis use and use disorders have been increasing in adult U.S. populations-with use and use disorders increasing more in medical relative to nonmedical legal cannabis states (38). Similar to the findings reported for adolescents, Hasin et al (39) also reports increasing rates of cannabis use and use disorder in blacks (relative to whites) and low-income individuals.…”

“…Key among these issues is whether, in fact, youth are being protected from cannabis in cannabis legal states. The good news, presented by Smart and Pacula (38), is that adolescent use and misuse of cannabis in the U.S. has remained stable or even decreased in cannabis legal states. This robust literature suggests that the outcomes predicted by legalization proponents-that cannabis regulation would make it more difficult for those under 18 years old (y/o) to obtain cannabis-has been successful.…”

“…This robust literature suggests that the outcomes predicted by legalization proponents-that cannabis regulation would make it more difficult for those under 18 years old (y/o) to obtain cannabis-has been successful. For college students, the findings are more uncertain, with some studies suggestion that use is increasing (38). As much of the epidemiologic data to-date consider individuals who are 18 to 20 year old "young adults" (39), it may be difficult to clearly parse out this population.…”

Assessing the public health impacts of legalizing recreational cannabis use: the US experience

“…It has taken time to produce dependable supplies of cannabis within states that have legalized, and there are a limited number of retail outlets available in a relatively small number of locations in these states 1 . For these reasons, evaluations of the first five or so years after legalization may provide a poor indication of the impacts of cannabis use on public health when the industry develops over a decade or more 42,77 .…”

“…We need more rigorous evaluations of the public health impacts of cannabis legalization 42 . Comparisons of differences between states in time series data on various causes of hospitalization and death are of limited value because they are not able to test alternative explanations of state level differences 77 . We also need large prospective studies of the effects of these policy changes on the use of cannabis and other drugs and their impact on health outcomes in individuals 42 .…”