Marijuana Regulation and Teen Use Rates

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.

“The percentage of adolescents reporting substance use decreased significantly in 2021, according to the latest results from the Monitoring the Future survey of substance use behaviors and related attitudes among eighth, 10th, and 12th graders in the United States. In line with continued long-term declines in the use of many illicit substances among adolescents previously reported by the Monitoring the Future survey, these findings represent the largest one-year decrease in overall illicit drug use reported since the survey began in 1975. …
Marijuana: The percentage of students who reported using marijuana (in all forms, including smoking and vaping) within the past year decreased significantly for eighth, 10th, and 12th grade students.

• Eighth graders: 7.1% reported using marijuana in the past year in 2021, compared to 11.4% in 2020
• 10th graders: 17.3% reported using marijuana in the past year in 2021, compared to 28.0% in 2020
• 12th graders: 30.5% reported using marijuana in the past year in 2021, compared to 35.2% in 2020.”

US National Institute on Drug Abuse, December 15, 2021 news release
“Using data from the YRBS [Youth Risk Behavior Survey] for the period 1993-2019, this study provides updated estimates of the association between legalization and adolescent marijuana use. … Consistent with estimates from prior studies, there was little evidence that RMLs [recreational marijuana laws] or MMLs [medical marijuana laws] encourage youth marijuana use.”

Association of marijuana legalization with marijuana use among US high school students, 1993-2019, JAMA Open Network, 2021
“The overall percentage of students who reported using marijuana at least 1 time during the previous 30 days in 2019 was not measurably different from the percentage in 2009 (21 percent)…. There was no measurable difference between 2009 and 2019 in the percentage of students who reported that illegal drugs were made available to them on school property.”

National Center for Education Statistics, Marijuana Use and Illegal Drug Availability, May 2021
“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.”

Medical marijuana laws (MMLs) and dispensary provisions not associated with higher odds of adolescent marijuana or heavy marijuana use: A 46 State Analysis, 1991-2015, Substance Abuse, 2021

“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.”

Trends in youth cannabis use across cannabis legalization: Data from the COMPASS prospective cohort study, Preventive Medicine Reports, 2021
“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.”

Post-legalization changes in marijuana use in a sample of young California adults, Addictive Behaviors, 2021
“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.”

Recreational marijuana legalization and adolescent use of marijuana, tobacco, alcohol. Journal of Adolescent Health, 2020
“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.”

Centers for Disease Control and Prevention, Prescription Opioid Misuse and Use of Alcohol and Other Substances Among High School Students — Youth Risk Behavior Survey, United States, 2019, 2020
“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.”

US Department of Health and Human Services, Key Substance Use and Mental Health Indicators in the United States: Results from the 2019 National Survey on Drug Use and Health, 2020
“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.”

Marijuana legalization and prevalence among adolescents, American Journal of Public Health, 2020
“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.”

Substance Abuse Mental Health Services Administration, Key Substance Use and Mental Health Indicators in the United States: Results from the 2018 National Survey on Drug Use and Health, 2019

“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.”

National Institutes on Drug Abuse, December 17, 2018 press release

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.”

Trends in perceived access to marijuana among adolescents in the United States: 2002-2015, Journal of Studies of Alcohol and Drugs, 2017
“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.”

United States Centers for Disease Control, National Estimates of Marijuana Use and Related Indicators – National Survey on Drug Use and Health, United States, 2002-2014, 2016

Rates of problematic cannabis use by young people has declined for the better part of the past two decades.

Adolescent treatment admissions for marijuana following recreational legalization in Colorado and Washington, Drug and Alcohol Dependence, 2020 | Declining Prevalence of Marijuana Use Disorders Among Adolescents in the United States, 2002 to 2013, Child & Adolescent Psychiatry, 2016 | See also: Recent Trends in the Prevalence of Marijuana Use and Associated Disorders in the United States, JAMA Psychiatry, 2016

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.”

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, The American Journal of Drugs and Alcohol Abuse, 2019
“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.”

A quasi-experimental evaluation of marijuana policies and youth marijuana use, The American Journal of Drug and Alcohol Abuse, 2019

“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.”

Has the legalisation of medical and recreational cannabis use in the USA affected the prevalence of cannabis use and cannabis use disorders? Current Addiction Reports
“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.”

Medical marijuana laws and adolescent marijuana use in the United States: A systematic review and meta-analysis, Addiction, 2018
“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.”

Medical marijuana availability, price, and product variety, and adolescent’s marijuana use, Journal of Adolescent Health, 2018
“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.”

U.S. epidemiology of cannabis use and associated problems, Neuropsychopharmacology, 2017
“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.”

Medical marijuana laws and adolescent use of marijuana and other substances: Alcohol, cigarettes, prescription drugs, and other illicit drugs. Drug and Alcohol Dependence, 2017
“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.”

Impact of medical marijuana laws on state-level marijuana use by age and gender, 2004-2013, Prevention Science, 2017
“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.”

Cannabis use and cannabis use disorders among youth in the United States, 2002-2014, Journal of Clinical Psychiatry, 2017
“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.”

Loose regulation of medical marijuana programs associated with higher rates of adult marijuana use but not cannabis use disorder, Addiction, 2017
“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.”

The design of medical marijuana laws and adolescent use and heavy use of marijuana: Analysis of 45 states from 1991 to 2011, Drug and Alcohol Dependence, 2017
“[N]o change in prevalence of use was found for 12-17 or 18-25 year-olds.”

State-level medical marijuana laws, marijuana use and perceived availability of marijuana among the general U.S. population, Drug and Alcohol Dependence, 2016
“[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.”

Prevalence of marijuana use does not differentially increase among youth after states pass medical marijuana laws: Commentary on and reanalysis of US National Survey on Drug Use in Households data 2002-2011, International Journal on Drug Policy, 2016
“[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.”

Medical marijuana laws and adolescent marijuana use in the USA from 1991 to 2014: results from annual, repeated cross-sectional surveys, Lancet Psychiatry, 2015
“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 Impact of State Medical Marijuana Legislation on Adolescent Marijuana Use, Journal of Adolescent Health, 2014

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

“This cannabis policy evaluation project adds novel evidence on a neglected parameter – namely, estimated occurrence of newly incident cannabis use for underage (<21 years) versus older adults. The project’s study populations were specified to yield nationally representative estimates for all 51 major US jurisdictions, with probability sample totals of 819,543 non-institutionalized US civilian residents between 2008 and 2019. … For those aged 12-20-years-old, the study estimates support the hypothesis that RCLs [recreational cannabis laws] did not affect the occurrence of newly incident cannabis use for underage persons.”

Estimating the effects of legalizing recreational cannabis on newly incident cannabis use, PLOS One, 2022
“Objectives: To examine the association between enactment of state RCLs [recreational cannabis laws] and changes in cannabis outcomes by race and ethnicity overall and by age groups in the US. … No changes were observed in any of the cannabis outcomes among participants aged 12 to 20 years of any racial or ethnic group.”

Racial and ethnic differences in cannabis use following legalization in US states with medical cannabis laws. JAMA Open Network, 2021
“Using data from the YRBS [Youth Risk Behavior Survey] for the period 1993-2019, this study provides updated estimates of the association between legalization and adolescent marijuana use. … Consistent with estimates from prior studies, there was little evidence that RMLs [recreational marijuana laws] or MMLs [medical marijuana laws] encourage youth marijuana use.”

Association of marijuana legalization with marijuana use among US high school students, 1993-2019, JAMA Open Network, 2021
“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.”

Association of marijuana laws with teen marijuana use: New estimates form the Youth Risk Behavior surveys, JAMA Pediatrics, 2019

“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.”

Has cannabis use among youth increased after changes in its legal status? A commentary on use of Monitoring the Future for analysis of changes in state cannabis laws, Preventive Medicine, 2019
“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.”

Trends and characteristics in marijuana use among public school students – King County, Washington, 2004-2016, Morbidity and Mortality Weekly Report, 2019
“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.”

Association of marijuana laws with teen marijuana use. JAMA Pediatrics, 2019
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.”

Colorado Division of Criminal Justice, Impacts of Marijuana Legalization in Colorado, 2018
“[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.”

Prevalence of cannabis use in youths after legalization in Washington state, JAMA Pediatrics, 2018
“[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.”

Adolescent marijuana use, marijuana-related perceptions, and use of other substances before and after initiation of retail marijuana sales in Colorado (2013-2015), Prevention Science, 2018
“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.”

Marijuana use and related health care encounters in Colorado before and after retail legalization, International Journal of Mental Health and Addiction, 2018
“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.”

“Colorado teen use hasn’t spiked,” Westword, June 21, 2018
“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.”

Comments from Colorado Gov. John Hickenlooper, April 9, 2018
“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.”

Comments from Larry Wolk, Chief Medical Officer of the Colorado Department of Public Health, October 23, 2017
“[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.”

Washington State Institute for Public policy, I-502 Evaluation and Cost-Benefit Analysis, 2017
“Following legalization, the rate of adolescent marijuana use in Colorado has fallen to its lowest level in nearly a decade.”

“Following marijuana legalization, teen drug use is down in Colorado,” Washington Post, 2017
“[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.”

Adolescent marijuana use and perceived ease of access before and after recreational marijuana implementation in Colorado, Substance Use & Misuse, 2017
“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.”

Colorado Department of Public Health and Environment, Monitoring Health Concerns Related to Marijuana in Colorado, 2017
[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).”

Lessons learned after three years of legalized, recreational marijuana: The Colorado experience, Preventive Medicine, 2017
“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.”

Marijuana use among young people in an era of policy change: what does recent evidence tell us?, The American Journal of Drug and Alcohol Abuse, 2016
“Recent trends in youth use (in Oregon from 2012 to 2015) have been stable.”

Oregon Health Authority, Marijuana use, attitudes and health effects in Oregon, 2016
“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.”

Adolescents’ Ease of Access to Marijuana Before and After Legalization of Marijuana in Washington State, 2016
“There is no conclusive evidence to show that policies in favor of medical and recreational cannabis use increase uptake by young people.”

Influence of legal status on the uptake of cannabis in young people, Current Opinion in Psychiatry, 2016