Places where recreational marijuana has been legalized may have a substantially lower incidence of teen use, according to a new study.

The surprising but not-shocking conclusion comes from a research letter published July 8 by the Journal of the American Medical Association Network’s JAMA Pediatrics.

The study notes that “repeated marijuana use during adolescence may lead to long-lasting changes in brain function that adversely affect educational, professional, and social outcomes.” Previous studies cited by the authors had “mixed” conclusions regarding recreational marijuana legalization.

In this study, the authors analyze the association between both medical and recreational legalization and use among teens, with “more policy variation captured than in any previous study in the literature.” The final sample size consists of more than 1.4 million subjects over the last 26 years.

The surprising result:

“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 in the Table showed that marijuana use among youth may actually decline after legalization for recreational purposes.”


The decline suggests that it may become more difficult for teenagers to obtain weed after street dealers are replaced with licensed dispensaries which require ID checks.

Supporting this, medical marijuana legalization was “not statistically associated” with an increase or decrease in marijuana use among youth at all. But states where recreational marijuana use had been legalized recorded an 8% decrease in the odds of marijuana use, and a 9% decrease in frequent marijuana use.

Last month Illinois became the 11th state in the US to legalize marijuana for recreational use, effective January 1, 2020.


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