Following the enactment of both medical cannabis access laws and adult use marijuana laws, there has not been any significant rise in self-reported marijuana use by adolescents.
“This natural-experimental study used state Youth Risk Behavior Survey (YRBS) data collected from participants in grades 9-12 from 1991 to 2015 in 46 states (N = 1,091,723). Taking advantage of heterogeneity across states in MML [medical marijuana law] status and MML dispensary design, difference-in-difference estimates compared states with enacted MMLs/dispensaries to non-MML/dispensaries states. … This study found no evidence between 1991 and 2015 of increases in adolescents reporting past 30-day marijuana use or heavy marijuana use associated with state MML enactment or operational MML dispensaries.”
“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.”
“The study was a secondary analysis of a longitudinal study of tobacco use among non-daily cigarette smokers. Participants were 563 young adults (aged 18–24) [in California] enrolled in 2015–16 and followed quarterly for 3 years. … Contrary to our expectations, frequency of marijuana use did not change significantly after legalization, and was stable throughout three years of observation. … In examining marijuana use before and after legalization of recreational sales in California, we found that frequency of use did not change significantly overall, including following legalization.”
“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.”
“Among adolescents aged 12 to 17, the percentage who were past year marijuana users decreased from 15.8 percent (or 3.9 million people) in 2002 to 13.2 percent (or 3.3 million people) in 2019.”
“Separating out the sum total effect of marijuana legalization from the many other influences on the attitudes and behaviors of adolescents is a difficult task. One way to approach this question with scientific rigor is to follow over time the prevalence of adolescent marijuana use in states that have and have not legalized marijuana use. ,,, 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 percentage of adolescents in 2018 who used marijuana in the past year was lower than the percentages in 2002 to 2004 and in 2009 to 2013, but it was similar to the percentages in 2005 to 2008 and in 2014 to 2017.”
“Rates of marijuana use by teens have been of great interest to researchers over the past decade, given major social and legislative shifts around the drug. … Fortunately, even as teens’ attitudes toward marijuana’s harms continue to relax, they are not showing corresponding increases in marijuana use.”
Perceived availability of marijuana among young people is falling nationwide
“Between 2002 and 2015, we observed a 27% overall reduction in the relative proportion of adolescents ages 12-17-and a 42 percent reduction among those ages 12-14-reporting that it would be “very easy” to obtain marijuana. This pattern was uniformly observed among youth in all sociodemographic subgroups. … Despite the legalization of recreational and medical marijuana in some states, our findings suggest that … perceptions that marijuana would be very easy to obtain are on the decline among American youth.”
“From 2002 to 2014, … the perceived availability decreased by 13 percent among persons aged 12-17 years and by three percent among persons aged 18-25 years.”
The enactment of medical cannabis laws is not associated with any causal upticks in youth marijuana use
“Based on current evidence, we largely concur with the conclusions of other reviews. Results for adolescents under age 18 are highly consistent in showing negative or insignificant effects of MCL (medical cannabis law) enactment on the prevalence of use. … The relatively few studies that considered the specific provisions of MCLs, such as allowances for dispensaries, have also found little evidence that such provisions matter for adolescent use outcomes.”
“This study sought to delineate associations between state-level shifts in decriminalization and medical marijuana laws (MML) and adolescent marijuana use. Using data on 861,082 adolescents (14 to 18+ years; 51% female) drawn from 1999 to 2015 state Youth Risk Behavior Surveys (YRBS), difference-in-differences models assessed how decriminalization and MML (medical marijuana legalization) policy enactment were associated with adolescent marijuana use, controlling for tobacco and alcohol policy shifts, adolescent characteristics, and state and year trends. … Neither policy was significantly associated with heavy marijuana use or the frequency of use. … [R]esults assuage concerns over potential detrimental effects of more liberal marijuana policies on youth use.”
“The evidence from large nationally representative surveys has not consistently demonstrated that MMLs (medical marijuana laws) have increased adolescent cannabis use. Adolescent use is higher in states that have passed MMLs, but this reflects higher rates of use before the passage of MMLs.”
“This systematic review screened 2999 unique papers retrieved from 17 sources, yielding 21 unique studies. Ultimately, 11 studies passed secondary exclusion criteria designed to ensure optimal study quality. … [A]ll estimates of pre–post changes in past-month marijuana use within MML (medical marijuana law) states from these studies were non-significant. … In summary, current evidence does not support the hypothesis that MML passage is associated with increased marijuana use prevalence among adolescents in states that have passed such laws.”
“We aimed to examine the availability of medical marijuana dispensaries, price of medical marijuana products, and variety of medical marijuana products in school neighborhoods and their associations with adolescents’ use of marijuana and susceptibility to use marijuana in the future. … The distance from school to the nearest medical marijuana dispensary was not associated with adolescents’ use of marijuana in the past month or susceptibility to use marijuana in the future, nor was the weighted count of medical marijuana dispensaries within the 3-mi band of school. Neither the product price nor the product variety in the dispensary nearest to school was associated with marijuana use or susceptibility to use. The results were robust to different specifications of medical marijuana measures. … There was no evidence supporting the associations of medical marijuana availability, price, or product variety around school with adolescents’ marijuana use and susceptibility to use.”
“Of 17 large surveys using difference-in-difference methods spanning different states, periods, and specifications, 16 indicated no MML (medical marijuana laws) effects on adolescent use. Despite differences in methodology, the findings were very consistent: post-MML adolescent cannabis use did not increase compared to pre-MML levels and to national trends in non-MML states during the corresponding years.”
“Among 8th graders, the prevalence of marijuana, binge drinking, cigarette use, non-medical use of opioids, amphetamines and tranquilizers, and any non-marijuana illicit drug use decreased after MML (medical marijuana laws)enactment. … MML enactment is associated with decreases in marijuana and other drugs in early adolescence in those states.”
“Past month MU (marijuana use) did not increase after enactment of MML (medical marijuana laws) in men or women ages 12–25. … There were no statistically significant increases in past-year MUD (marijuana use disorder) prevalence for any age or gender group after MML enactment.”
“The prevalence of past-year cannabis use among youth decreased from 15.8 percent in 2002 to 13.1 percent in 2014. … Among youth cannabis users, the prevalence of past-year CUD (cannabis use disorder) decreased from 27.0 percent in 2002 to 20.4 percent in 2014.”
“Models adjusted for national trends showed no significant change in the prevalence of past-month marijuana use among adolescents or young adults (those ages 18-25) after the enactment of MMLs. … Our results did not show evidence of increased prevalence of Cannabis Use Disorder (abuse and/or dependence according to DSM-IV criteria) among adolescents or adults after states enacted MMLs.”
“Using data through 2011, this study found little evidence for an increase in past-30-
day marijuana use, or past-30-day heavy marijuana use, among adolescents in response to state-enacted medical marijuana laws, regardless of most provisions, consistent with findings from other recent studies.”
“[W]hen within-state changes are properly considered and pre-MML (medical marijuana law) prevalence is properly controlled, there is no evidence of a differential increase in past-month marijuana use in youth that can be attributed to state medical marijuana laws.”
“[T]he results of this study showed no evidence for an increase in adolescent marijuana use after the passage of state laws permitting use of marijuana for medical purposes. … [C]oncerns that increased marijuana use is an unintended effect of state marijuana laws seem unfounded.”
“There were no statistically significant differences in marijuana use before and after policy change for any state pairing. In the regression analysis, we did not find an overall increased probability of marijuana use related to the policy change. … This study did not find increases in adolescent marijuana use related to legalization of medical marijuana.”
The passage of adult use cannabis laws is not associated with any causal upticks in youth marijuana use in those jurisdictions that have enacted them
“Consistent with the results of previous researchers, there was no evidence that the legalization of medical marijuana encourages marijuana use among youth. Moreover, the estimates reported showed that marijuana use among youth may actually decline after legalization for recreational purposes.”
“Using the Washington Health Youth Survey, we estimate that after recreational cannabis legalization past 30-day cannabis use prevalence in grade 8 decreased by 22.0%, in grade 10 prevalence decreased by 12.7%, and no effect in grade 12. These trends are consistent with those in states without recreational cannabis laws, suggesting that legalization did not impact adolescent use prevalence.”
“Despite legalization of the retail sale of marijuana to adults in Washington in 2012, evidence from the biennial Washington State Healthy Youth Survey indicates that the prevalence of past 30-day marijuana use among students in grades 10 and 12 began to decline that year. The decline continued in 2016 among grade 10 students and did not change significantly among grade 12 students.”
“In the fully adjusted models, MMLs (medical marijuana laws) were not statistically associated with either measure of marijuana use, but RMLs (recreational marijuana laws) were associated with an 8% decrease in the odds of marijuana use and a 9% decrease in the odds of frequent marijuana use. … Consistent with the results of previous researchers, there was no evidence that the legalization of medical marijuana encourages marijuana use among youth. Moreover, the estimates reported … showed that marijuana use among youth may actually decline after legalization for recreational purposes. This latter result is consistent with … the argument that it is more difficult for teenagers to obtain marijuana as drug dealers are replaced by licensed dispensaries that require proof of age.”
There has been “no significant change in past 30-day use of marijuana between 2013 (19.7%) and 2017 (19.4%). Also, in 2017, the use rates were not different from the national 30-day use rates reported by the Youth Risk Behavior Survey. In 2017, 19.4% of Colorado high school students reported using marijuana in the past 30-days compared to 19.8% of high school students nationally that reported this behavior.”
“[T]he HYS (Washington Healthy Use Survey) shows statistically significant declines in (marijuana use) prevalence from 2010-2012 to 2014-2016 among both 8th graders (from 9.8% to 7.3%) and 10th graders (from 19.8% to 17.8%). Neither MTF (Monitoring the Future survey) nor HYS analysis showed changes among 12th graders.”
“[W]e did not find a significant effect for perceived wrongfulness, perceived ease of access, or perceived parental disapproval. We did not find significant variability in past 30-day use by demographic characteristics or by school and community factors from 2013 to 2015. We did not find a significant effect associated with the introduction of legal sales of recreational marijuana to adults in Colorado on adolescent (illegal) use.”
“With legalization of retail marijuana in Colorado, and the opening of dispensaries in January 2014, two key questions were how legalization would impact marijuana use and whether there would be an increase in adverse health events. Legalization did not noticeably impact marijuana use rates among adolescents or young adults. Past-30-day use among adolescents remained steady for more than ten years, pre- and post-legalization.”
“According to the 2017 data [provided by the U.S. Centers for Disease Control and Prevention’s High School Youth Risk Behavior Survey,] the most recent available, 19.6 percent of Colorado high school students currently use marijuana — a couple of ticks below the national average of 19.8 percent. Moreover, the latest Colorado numbers are well below the 21.2 percent registered in 2015, the year after recreational sales went into effect, and 22 percent circa the pre-legalization year of 2011. As for lifetime use of marijuana among Colorado high-schoolers, it fell to 35.5 percent, a little under the 35.6 percent national average. The Colorado figures from 2015 and 2011 were 38 percent and 39.5 percent, respectively.”
“Certainly the worst things that we had great fear about (the legalization of marijuana for adults in Colorado) – spikes in consumption, kids, people driving while high – we haven’t seen any of that. We saw a little increase in teenagers and that came down within a couple years. … We were very worried that by legalizing, we were making this more somehow more psychologically available to kids. We haven’t seen that. If anything, we’ve seen less drug dealers.”
“I think the concern was that by legalizing marijuana, we should certainly see an increase in adult use, and maybe that would leak into our youth. [There was also a concern that] youth would somehow gain greater access, and/or feel entitled to go ahead and use in greater numbers. We just haven’t seen that pan out. … It appears that teenagers make decisions to consume marijuana for reasons other than legalization—like they do with other risk behaviors.”
“[A]cross grades 6, 8, 10, and 12, cannabis use indicators have been stable or fallen slightly since I-502’s enactment. … We found no evidence that the amount of legal cannabis sales affected youth substance use or attitudes about cannabis or drug-related criminal convictions.”
“[T]he presence of recreational marijuana retail store(s) was not associated with perceived easy access to marijuana, controlling for perceived ease of access before the retail sales. There was no significant change in past 30-day marijuana use in bivariate analysis or in a multivariate model including presence of a recreational marijuana store.”
“For adults and adolescents [in Colorado], past-month marijuana use has not changed since legalization either in terms of the number of people using or the frequency of use among users. Based on the most comprehensive data available, past month marijuana use among Colorado adolescents is nearly identical to the national average.”
[M]arijuana use, both among adults and among youth [in Colorado], does not appear to be increasing to date. No change was observed in past 30-day marijuana use among adults between 2014 (13.6 percent) and 2015 (13.4 percent). Similarly, there was no statistically significant change in 30-day or lifetime marijuana use among high school students between 2013 (lifetime: 36.9 percent, 30-day: 19.7 percent) and 2015 (lifetime: 38.0 percent, 30-day: 21.2 percent).”
“We can state with some confidence that, even in states that have enacted marijuana liberalization policies, marijuana use among adolescents is not currently increasing. In fact, there is rather compelling evidence that adolescent marijuana use has steadily declined.”
“Despite concerns that legalization of marijuana for recreational use by adults in 2012 may also increase teens’ ability to access to marijuana [in Washington], preliminary analyses of state-wide HYS (Healthy Youth Survey) data suggest otherwise.”
