The clouded debate: A systematic review of comparative longitudinal studies examining the impact of recreational cannabis legalization on key public health outcomes

Abstract

BackgroundIneffective cannabis regulatory frameworks such as prohibition have sparked interest in alternative solutions to reduce individual and societal harms. While it has been suggested that the recreational legalization process has yielded early successes, the relatively recent implementation of the novel policies has provided a modest time frame for a truly thorough establishment and assessment of key population-level indicators. The following systematic review focuses on identifying the downstream public health sequelae of cannabis legalization policies, including parameters such as cannabis consumption rates, hospitalization rates, vehicular accidents and fatalities, criminal activity, and suicidal behaviors, as well as other substance use trends.MethodsAn exhaustive search of the MEDLINE and Google Scholar databases were performed to identify high-quality (1) longitudinal studies, which (2) compared key public health outcomes between regions which had and had not implemented recreational cannabis legalization (RML) policies, (3) using distinct databases and/or time frames. Thirty-two original research articles were retained for review.ResultsAdult past-month cannabis consumption (26+ years) seems to have significantly increased following RML, whereas young adult (18–26 years) and adolescent (12–17 years) populations do not show a significant rise in past-month cannabis use. RML shows preliminary trends in increasing service use (such as hospitalizations, emergency department visits, or poisonings) or vehicular traffic fatalities. Preliminary evidence suggests that RML is related to potential increases in serious/violent crimes, and heterogeneous effects on suicidal behaviors. While the research does not illustrate that RML is linked to changing consumptions patterns of cigarette, stimulant, or opioid use, alcohol use may be on the rise, and opioid prescribing patterns are shown to be significantly correlated with RML.ConclusionThe current data supports the notion that RML is correlated with altered cannabis consumption in adults, potentially increased criminal activity, and a decline in opioid quantities and prescriptions provided to patients. Future work should address additional knowledge gaps for vulnerable populations, such as individuals with mental health problems or persons consuming cannabis frequently/at higher THC doses. The effects of varying legalization models should also be evaluated for their potentially differing impacts on population-level outcomes.

Cannabis Use Frequency and Cannabis-Related Consequences in High-Risk Young Adults Across Cannabis Legalization

“…At a broader level, a limitation of these findings is the lack of a control group to evaluate cannabis legalization as a natural experiment more fully. Although we principally observed decreases in use and problems, it is still possible that legalization attenuated or otherwise altered the patterns we might have observed in absence of this policy change, and future research may consider matching available Canadian data to an appropriate control jurisdiction to examine legalization as a natural experiment . This study also focused only on the initial policy change legalizing dried flower products; the legalization of cannabis edibles and concentrate products could have differential impacts not captured in this study.…”

“…Although some studies have found that cannabis use (and frequency of use) increased among youths and young adults following legalization, most studies have not found a pronounced or statistically significant increase . Conversely, evidence suggestions that there have been some impacts on public health more broadly, including increases in incidence of youth hospitalizations and emergency department visits related to cannabis use and increased cannabis-related traffic fatalities …”

“…Moreover, there have been few longitudinal studies examining the impact of legalization, which represents a substantial research gap. Longitudinal data provide richer information than repeated cross-sectional surveys, allowing for characterization of within-person changes, the comparison of trajectories of cannabis use, estimation of rates of change, and moderators of changes, such as prelegalization cannabis use status, sex, or income . The purpose of this study was to address these research gaps by examining the association of cannabis legalization with cannabis use frequency and cannabis-related consequences using longitudinal data from a cohort of young adults who already used substances prelegalization.…”

Effects of cannabis regulation in Switzerland: Study protocol of a randomized controlled trial

“…Some studies have shown an association between the regulation of cannabis for recreational use and increased frequency of cannabis use among adults ( 15 , 16 ), whereas others have shown no relation or a relation with increased three-month prevalence ( 21 , 22 ). A recent systematic review has suggested that past-month cannabis use in adults (> 26 years) has increased after recreational cannabis legalization, whereas young adults (18–26 years) and adolescents (12–17 years) did not show an increase in past-month cannabis use ( 86 ). However, existing evidence is mainly based on observational data evaluating pre-post-legalization or comparisons between states with and without cannabis legalization.…”

“…A risk-based monitoring will be conducted to ensure the quality control. Based on the "Guidelines for risk-based monitoring, " the risk was estimated low (85). The study investigators conducted an initiation visit at the study center before eligibility screenings have started.…”