Cannabis use among teens has declined in states with legal recreational marijuana, according to a new paper published in the medical journal JAMA Pediatrics. Researchers found that in states with legal adult-use cannabis, there was an 8% drop in the number of youths who said they used marijuana within the last 30 days and a 9% drop in the number of high-schoolers who said that they had used at least 10 times in the past 30 days.
The research was led by D. Mark Anderson, an economist at Montana State University, along with colleagues from the University of Colorado, the University of Oregon, and San Diego University. Researchers analyzed data that spanned 25 years, from 1993 to 2017, that included data from about 1.4 million high school students. The data was collected by the US Centers for Disease Control and Prevention’s annual Youth Risk Behavior Surveys, which are administered to students every two years.
Researchers did not find a significant decrease in teen marijuana use in states with legal medical cannabis.
“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 [by the Youth Risk Behavior Surveys] showed that marijuana use among youth may actually decline after legalization for recreational purposes.”
The researchers acknowledged that while there’s an association between legal adult-use marijuana, there isn’t a causal connection.
“Because many recreational marijuana laws have been passed so recently, we do observe limited post-treatment data for some of these states,” Anderson said. “In a few years, it would make sense to update our estimates as more data become available.”
One possible reason for the decline in teen pot use is that a regulation cannabis market reduces the availability of black market marijuana. In states where recreational marijuana is legal, “it is more difficult for teenagers to obtain marijuana as drug dealers are replaced by licensed dispensaries that require proof of age.”
Nationally, teen cannabis use has increased from 0.6% in 1991 to 6.3% in 2017, according to a study published in the American Journal of Public Health.