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Fewer adolescents smoke cannabis in countries where legalization is allowed

In-depth study of 1,4 million schoolchildren in the United States between 1993 and 2017

In the United States, 33 states have passed medical cannabis laws and 10 states have legalized recreational use. Most lawmakers are particularly concerned that this legalization will encourage drug use among young people, namely that repeated drug use in adolescence may result in changes in cognitive function and intellectual and can have negative effects on academic, professional and social outcomes.

A recent study, published in the Journal of the American Medical Association (JAMA Pediatrics), examined data on cannabis use among 1,4 million schoolchildren in the United States between 1993 and 2017, from questionnaires completed by the young people themselves from the investigations Annual National Youth at Risk Behavior of the U.S. Centers for Disease Prevention and Control. Researchers took a close look at self-reported consumption among students, as well as responses to these surveys in legalized areas. The review of the responses took place before and after the application of legalization laws.

These surveys are submitted every two years to U.S. high school students (Grades 9 to 12) and are used by government agencies to track trends in activity and substance use behaviors. Data analysis began in December 2018. Institutional review board approval and participant consent were not required due to the secondary nature of the data. However, this meta-analysis concludes that the results of previous studies did not support the hypothesis that medical cannabis increases consumption among young people, while the evidence for the effects of recreational cannabis laws is mixed. 

Multivariate logistic regression analysis was used to estimate associations between medical and recreational legalization and the likelihood of use in the past 30 days. Frequent consumption (i.e. at least 10 times in the last 30 days) was also taken into account. Two-sided hypothesis tests were used and the results were considered statistically significant. All analyzes were performed with the Stata statistics software.

Youth consumption may actually be falling

These 24-year statistical data show that consumption in countries where cannabis is legal decreases by 8% among young smokers who use at least once a month and among college students who smoke regularly a drop of 9%. This volume of data makes it the most comprehensive study in its field.

Mark Anderson

“Because our study relies on more political variations than previous work, we consider our estimates to be the most credible to date”

said Mark Anderson, associate professor at the Montana State University of Bozeman and first author of the study

Why are these national data sets seeing large enough declines when other studies find no difference?

Logistical estimates of the association of legalization of marijuana with adolescent marijuana
Logistical estimates of the association of legalization with adolescent use
MML = legal medical cannabis
MLR = legal recreational cannabis

Consistent with the results of previous researchers, there is no evidence that legalization encourages drug use among young people. Additionally, the estimates presented in this table show that youth use may actually decrease after recreational legalization. This last result is consistent with Dilley's conclusions of 2018 and the argument that it's harder for teens to get weed as drug dealers are replaced by licensed dispensaries that require ID.

These conclusions are, of course, the opposite of the arguments of those who oppose legalization and argue that allowing a legal marijuana market for adults will necessarily result in an increase in cannabis use among young people.

Tags : AdolescentConsumptionDrugEtudeJAMASearchstatisticalUS
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