Marijuana Regulation: Impact on Health, Safety, Economy


The enactment of adult use cannabis regulation is not associated with significant upticks in marijuana use by adolescents

  • “Canada legalized recreational cannabis use for adults on October 17, 2018 with decision-makers emphasising the need to reduce cannabis use among youth. We sought to characterize trends of youth cannabis use before and after cannabis legalization by relying on a quasi-experimental design evaluating cannabis use among high school students in Alberta, British Columbia, Ontario, and Québec who participated in the COMPASS prospective cohort study. Overall trends in use were examined using a large repeat cross-sectional sample (n=102,685) at two time points before legalization (16/17 and 17/18 school years) and one after (18/19 school year). … In the longitudinal sample, no significant differences in trends of cannabis use over time were found between cohorts for any of the three use frequency metrics. Therefore, it appears that cannabis legalization has not yet been followed by pronounced changes on youth cannabis use.”
  • “Youth Risk Behavior Survey data from 47 states from 1999 to 2017 assessed marijuana, alcohol, cigarette, and e-cigarette use among adolescents (14-18+ years; N = 1,077,938). Associations between RML (recreational marijuana legalization) and adolescent past-month substance use were analyzed using quasi-experimental difference-in-differences zero-inflated negative binomial models. … Controlling for other state substance policies, year and state fixed effects, and adolescent demographic characteristics, models found that RML was not associated with a significant shift in the likelihood of marijuana use. … Results suggest minimal short-term effects of RML on adolescent substance use, with small declines in marijuana use.”
  • “This report provides key insights into substance use behaviors of U.S. high school students during 2009–2019. Encouraging findings include decreasing prevalence of current alcohol use and decreases in the prevalence of lifetime use of marijuana. … Lifetime marijuana use increased during 2009–2013 and then decreased during 2013–2019. … The findings in this report indicate that youth substance use has declined in recent years.”
  • “Taken as a whole, these studies suggest that marijuana legalization has not had much overall effect on marijuana use by children and adolescents, at least during the past two decades. From 2000 to 2019, marijuana legalization changed substantially, and now medical marijuana is legal in 33 states and recreational marijuana use in 11. Despite these changes, adolescent marijuana prevalence has varied little, with the national percentage of US 12th graders who have ever used marijuana hovering within a narrow window of 42% to 49% during this time period.1 In 2019, it was at 44%, toward the lower end of this range. … In summary, prevalence of marijuana use among adolescents has remained remarkably steady over the past 20 years despite substantial changes in its legality across the United States during this period.”

The establishment of cannabis retailers is not associated with upticks in criminal activity

  • “This paper studies the effects of marijuana legalization on neighborhood crime and documents the patterns in retail dispensary locations over time using detailed micro-level data from Denver, Colorado. … The results imply that an additional dispensary in a neighborhood leads to a reduction of 17 crimes per month per 10,000 residents, which corresponds to roughly a 19 percent decline relative to the average crime rate over the sample period. … Overall, our results suggest that dispensaries cause an overall reduction in crime in neighborhoods, with no evidence of spillovers to surrounding neighborhoods. … Our results are consistent with theories that predict that marijuana legalization will displace illicit criminal organizations and decrease crime through changes in security behaviors or substitution toward more harmful substances. … Lastly, there is no evidence that increased marijuana use itself results in additional crime.”
  • “Using 2010 to 2015 Uniform Crime Reports data, the research undertakes interrupted time-series analysis on the offenses known to be cleared by arrest to create monthly counts of violent and property crime clearance rate as well as disaggregated counts by crime type. Findings suggest no negative effects of legalization on crime clearance rates. Moreover, evidence suggests some crime clearance rates have improved. Our findings suggest legalization has resulted in improvements in some clearance rates.”

Medical cannabis access laws are not associated with adverse effects on traffic safety

  • “While attention has been given to how legalization of recreational cannabis affects traffic crash rates, there was been limited research on how cannabis affects pedestrians involved in traffic crashes. This study examined the association between cannabis legalization (medical, recreational use, and recreational sales) and fatal motor vehicle crash rates (both pedestrian-involved and total fatal crashes). … We found no significant differences in pedestrian-involved fatal motor vehicle crashes between legalized cannabis states and control states following medical or recreational cannabis legalization. Washington and Oregon saw immediate decreases in all fatal crashes (-4.15 and -6.60) following medical cannabis legalization. … Overall findings do not suggest an elevated risk of total or pedestrian-involved fatal motor vehicle crashes.”
  • “This paper reports a quasi-experimental evaluation of California’s 1996 medical marijuana law (MML), known as Proposition 215, on statewide motor vehicle fatalities between 1996 and 2015. … We found that legalizing medical marijuana in California led to a sustained reduction in statewide motor vehicle fatalities. … California’s 1996 MML appears to have produced a large, sustained decrease in statewide motor vehicle fatalities amounting to an annual reduction between 588 and 900 vehicle fatalities.”

Adult-use marijuana laws have generally been associated with few changes in traffic safety, though more recent studies have yielded less consistent findings

  • “A retrospective analysis of data collected at trauma centers in Arizona, California, Ohio, Oregon, New Jersey, and Texas between 2006 and 2018 was performed. … The data were analyzed to evaluate the trends in THC and alcohol use in victims of MVC [a motor vehicle crash], related to marijuana legalization. … There did not appear to be a relationship between the legalization of marijuana and the likelihood of finding THC in patients admitted after MVC. … There was no apparent increase in the incidence of driving under the influence of marijuana after legalization.”
  • “[The] implementation of recreational cannabis laws was associated with increases in traffic fatalities in Colorado but not in Washington state. … Findings suggest that adverse unintended effects of recreational cannabis laws can be heterogeneous and may depend on variations in implementation of these laws (e.g., density of recreational cannabis stores).”
  • “In the five years after legalization, fatal crash rates increased more in Colorado and Washington than would be expected had they continued to parallel crash rates in the control states (+1.2 crashes/billion vehicle miles traveled, but not significantly so. The effect was more pronounced and statistically significant after the opening of commercial dispensaries. … [This finding]… stands in contrast to earlier studies finding decreases in traffic fatalities following medical marijuana legalization. … [T]hese unexpected findings raise the possibility that legalization of medical and recreational marijuana represent two distinct policy exposures rather than ‘escalating doses’ of the same exposure and pose very different risks. This is an area in need of further study.”

Marijuana regulation is not associated with adverse effects on workplace performance or safety

  • “We evaluate the effect of RMLs [recreational marijuana laws] on WC [workers’ compensation] benefit receipt and WC income over the period 2010 to 2018 using the Annual Social and Economic Supplement (ASEC) of the Current Population Survey (CPS). … Our results show a decline in WC benefit propensity of 0.18 percentage points (‘ppts’), which corresponds to a 20.0% reduction in any WC income, after states legalize marijuana for recreational use. Similarly, we find that annual income received from WC declines by $21.98 (or 20.5%) post-RML. These results are not driven by pre-existing trends. … The present study provides empirical evidence on the consequences of marijuana legalization on issues related to the labor market outcomes, in particular, WC claiming of older adults. … Our findings suggest potentially important benefits to older workers and society at large. Broadly, we show non-trivial improvements in work capacity, which we proxy with WC benefit receipt and various other metrics in our mechanism analysis, among older adults.”
  • “[T]he current body of evidence does not provide sufficient evidence to support the position that cannabis users are at increased risk of occupational injury.”
  • “We study the effect of state medical marijuana laws (MMLs) on workers’ compensation (WC) claiming among adults. … We use data on claiming drawn from the Annual Social and Economic supplement to the Current Population Survey over the period 1989 to 2012, coupled with a differences‐in‐differences design to provide the first evidence on this relationship. Our estimates show that, post MML, WC claiming declines, both the propensity to claim and the level of income from WC. These findings suggest that medical marijuana can allow workers to better manage symptoms associated with workplace injuries and illnesses and, in turn, reduce need for WC.”
  • “There is no or insufficient evidence to support … a statistical association between cannabis use and occupational accidents or injuries.”
  • Reducing criminal penalties for marijuana offenses is associated with increased probability of employment, particularly for young males, and an average increase of 4.5 percent in weekly earnings. “This data provides suggestive evidence that marijuana decriminalization laws improve extrinsic labor market outcomes. … This result is consistent with existing literature that suggests black adults, especially men, stand to benefit the most from removing these penalties.”

Marijuana regulation is associated with declining alcohol consumption

  • “We use data on purchases of alcoholic beverages in grocery, convenience, drug, or mass distribution stores in US counties for 2006-2015 to study the link between medical marijuana laws and alcohol consumption and focus on settling the debate between the substitutability or complementarity between marijuana and alcohol. … We find that the legalization of medical marijuana reduces alcohol consumption. We find consistent evidence across different specifications and alcohol products (i.e. alcohol in general, beer and wine). States legalizing medical marijuana use experience significant decrease in the aggregate sales of alcohol, beer and wine. Moreover, the effects are not short lived, with significant reductions observed up to 24 months after the passage of the law.”
  • “Research firm Cowen & Company analyzed the state of the beer industry in Colorado, Oregon and Washington–states where both recreational weed is legal and craft beer has become popular. In those states, beer markets have “collectively underperformed” over the last two years, trailing behind beer sales around the country.”

Marijuana regulation is associated with increased tax revenue and job creation