Since 2002, perceived availability of marijuana among young people has fallen dramatically 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."
The enactment of medical cannabis laws is not associated with any causal upticks in youth marijuana use
"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."
"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
"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."