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 legislators are particularly concerned that this legalization encourages youth consumption to know that repeated teenage 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 the use of cannabis among 1,4 million schoolchildren in the United States between 1993 and 2017, based on questionnaires completed by young people themselves from investigations National Annuals on the Behavior of Youth at Risk in US Centers for Disease Prevention and Control. The researchers closely examined the self-reported consumption among students, as well as the responses to these surveys in the legalized areas. The examination of the answers was done before and after the application of the laws on legalization.

These surveys are submitted every two years to US high school students (9e to 12e year) and are used by government agencies to monitor trends in activity and substance use behavior. Data analysis started in December 2018. Institutional Review Committee approval and consent was not required due to the secondary nature of the data. However, this meta-analysis concluded that the results of previous studies did not support the hypothesis that medical cannabis would increase youth use, while evidence of the effects of recreational cannabis laws is mixed.

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A multivariate logistic regression analysis was used to estimate the associations between medical and recreational legalization and the probability of consumption during the last 30 days. Frequent consumption (ie at least 10 times during the last 30 days) has also been taken into account. Bilateral hypothesis tests were used and the results were considered statistically significant. All analyzes were done with the Stata statistics software.

Youth consumption may actually be falling

These statistical data on 24 years reveal that consumption in countries where cannabis is legal decreases by 8% in young smokers consuming at least once a month and among students who regularly smoke a decrease of 9%. This volume of data makes it the most complete study in its field.

Mark Anderson

"Because our study is based on more political variations than previous work, we consider our estimates as the most credible to date"

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

Why do we see significant reductions in this national dataset, while other studies find no difference?

Logistical estimates of the association of the legalization of marijuana with marijuana in adolescence
Logistic estimates of the association of legalization with consumption in adolescents
MML = legal medical cannabis
MLR = legal recreational cannabis

Consistent with findings of previous researchers, there is no evidence that legalization encourages consumption among youth. In addition, the estimates presented in this table show that consumption among youth may actually decrease after legalization for recreational purposes. This last result is consistent with Dilley's conclusions from 2018 and the argument that it is harder for teens to get weed because drug traffickers are being replaced by licensed clinics that require the presentation of an ID card.

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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 : AdolescentConsumptionDrugÉtudeJAMASearchstatisticalUS