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A Study That Found Cannabis Legalization Doesn’t Encourage Teens to Use the Drug Has Been Retracted

By Leo Bear-McGuinness

Published: Mar 10, 2022   
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Last September, a study was published in JAMA Network Open that found that cannabis legalization doesn’t seem to encourage adolescents to use the drug.

But this study has now been retracted.

By October, at least two readers of the original paper had noted that some of the researchers’ methods were flawed. After accepting these critiques, the authors have retracted their paper and replaced it with a corrected version.

Despite this change, the study’s key conclusion, that cannabis legalization doesn’t seem to encourage adolescent use of the drug, remains intact.

Mistakes were made

Among policy makers and campaigners, one of the main concerns surrounding cannabis legalization has been that the policy could inadvertently lead to more cannabis use among children and teenagers.

To test this hypothesis, the researchers from Montana State University sifted through an existing youth behavior survey to find data on teen cannabis use pre-legalization and post-legalization in 10 US states.

After some statistical analysis, the research team found no evidence that cannabis legalization encouraged adolescent cannabis use.

“Consistent with estimates from prior studies, there was little evidence that RMLs [recreational marijuana laws] or MMLs [medical marijuana laws] encourage youth marijuana use,” the study authors concluded in their paper published last September.

Furthermore, the team actually found that medical cannabis legalization was associated with a 6 percent decrease in the odds of current teen cannabis use and a 7 percent decrease in the odds of frequent use in the years following medical cannabis law adoption. There was an observed decrease in the odds of cannabis use post-recreational legalization, too.

However, these latter findings were quickly called into question after the paper’s publication.

At least two commentators noted that the Montana researchers had pooled national and state data from the youth behavior survey. As there is some overlap between the two data sets, some adolescents could therefore have been represented more than once in the researchers’ results.

In a letter published in JAMA Network Open on March 8 this year, the Montana researchers acknowledged these errors and accepted the retraction of the original paper.

“We apologize to the readers and editors of JAMA Network Open for any confusion we caused by conducting our prior analysis based on unweighted and pooled data,” they wrote.

At the request of the JAMA editors, the researchers have since replaced the original study with an updated version that worked from un-pooled survey data, and this updated paper did come to slightly different conclusions.

While the main finding – that cannabis legalization doesn’t seem to encourage adolescent cannabis use – remained intact, the secondary finding – that both medical and recreational cannabis legalization were linked with a small decline in teen cannabis use – disappeared.

“We had previously reported that medical marijuana law (MML) adoption was associated with a statistically significant decrease in the odds of marijuana use among adolescents and that 2 or more years after adoption, recreational marijuana laws (RMLs) were associated with a statistically significant decrease in the odds of marijuana use among adolescents,” the researchers wrote in their retraction letter.

“After reconducting the analyses with weighted and unpooled data, RML adoption and MML adoption were no longer statistically significantly associated with adolescent marijuana use.”

Youth use

The study isn’t the first from the Montana researchers to unfound the idea that cannabis legalization leads to more teenage drug use.

In a paper published in 2019, the same researchers found that states that legalized recreational cannabis were associated with an 8 percent fall in the number of teenagers who claimed they used cannabis in the last 30 days, and a 9 percent drop in the number who said they’d consumed the drug at least 10 times in the last 30 days.

“I think the big takeaway is that we find no evidence that teen marijuana use goes up after legalization for medicinal or recreational purposes,” Mark Anderson, an associate professor at Montana State University and lead author of the study, told Analytical Cannabis at the time.

“We view this as a very important result from a policy perspective because opponents often claim that teen use will skyrocket after these laws are passed. Based on our analysis, this has simply not been the case.”

However, as this 2019 study also pooled data from the same national youth behavior survey just as the 2021 study did, its conclusions may also be brought into question.

Elsewhere in cannabis-youth research, other researchers have found that adolescent cannabis use is on the rise.

In a paper published last October in JAMA Pediatrics, a team from the University of Queensland, Australia, found that the proportion of teens who admit to vaping cannabis more than doubled between 2013 and 2020, from 6.1 percent to 13.6 percent.

Another study published in 2019 came to a similar conclusion, finding that the prevalence of students using cannabis e-cigarette rose from 11.1 percent in 2017 to 14.7 percent in 2018.

And a recent survey study published in the Journal of Studies on Alcohol and Drugs found significant increases in lifetime and past-30-day cannabis use among nearly all demographic groups post-legalization in California.


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