Adolescent cannabis use has long been a concern for users and activists of the drug.

Despite the proven benefits of medical marijuana and the low severity of its negative side effects, many studies have found connections between cannabis use in teens and changes in their brain matter. A new study adds another layer to the discussion, suggesting that this might not be entirely true.

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Published in the journal Drug and Alcohol Dependance and conducted by researchers from Arizona State University, the study tracked the cannabis use of 200 boys with conduct issues in Pittsburgh during the late 80s. Researchers compared the subjects’ consumption rates with brains cans that were taken 20 and 30 years later. There was no apparent difference in brain structure.

“Even boys with the highest level of cannabis exposure in adolescence showed subcortical brain volumes and cortical brain volumes and thickness in adulthood that were similar to boys with almost no exposure to cannabis throughout adolescence,” say the authors of the research.

While the study has some drawbacks, like the small sample size and the fact that MRI scans might not be the most effective way of seeing the effects of cannabis on the brain, it does provide some valuable information and an interesting perspective.

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Madeline Maier, lead author of the study and director of ASU’s substance use, health and behavior lab, says that the most significant part of the study is that it follows other researches in suggesting that cannabis’ influence on young brains isn’t permanent. “Reviews of these studies have revealed that, although a few studies have found evidence of an association between an earlier age-of-onset of cannabis use and adult brain structure, most studies have not.”