Concerns surrounding marijuana use among adolescents have long been a hurdle for legalization advocates, given that the brains of children are developing at a rapid rate. But a new study suggests that cannabis may not pose much long-term risk on brain function at all.
The study, to be published in next month’s issue of Drug and Alcohol Dependence and conducted by researchers at Arizona State University, “tested associations between prospectively-assessed trajectories of adolescent cannabis use and adult brain structure in a sample of boys followed to adulthood.” In an effort to test the hypothesis that adolescent marijuana users demonstrate structural alterations to their brains in adulthood, the researchers analyzed self-reported cannabis use among boys aged 13-19 in Pittsburgh.
The group of around 1000 boys was examined during the 1980s. When certain “adolescent cannabis trajectories” were identified by the researchers, the boys were classified based on four different trajcetories: non-users/infrequent users, desisters, escalators, and chronic-relatively frequent users. “Boys in different trajectory subgroups did not differ on adult brain structure in any subcortical or cortical region of interest,” the researchers wrote in their analysis of the results.
Additionally, there was a subset of 181 of the boys which subsequently underwent structural neuroimaging in adulthood when they were between the ages of 30-36. That subset was then tested to identify any differences in adult brain structure.
In conclusion, the researchers said that “[a]dolescent cannabis use is not associated with structural brain differences in adulthood.” They added: “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.”
The research, which was led by Madeline Meier, the director of Arizona State University’s Substance Use, Health and Behavior Lab, is just the latest in a slew of recent studies that analyze the long-term effects of cannabis use. As legalization spreads across America and throughout the world, the calls for sound, academic research on pot use—which has long been lacking—have intensified. In April, the cannabis investor Charles R. Broderick responded to that dearth of research with a $9 million donation to Harvard and MIT to support studies into the science of cannabinoids. It was the largest donation to date to promote research of that kind. Broderick said the gift was driven by a desire “to fill the research void that currently exists in the science of cannabis.”
In that same spirit, a study last month examined why marijuana makes some users anxious, while others experience joy and euphoria.