Marijuana May Change Your Brain if You Smoke as a Teen

First Posted: Feb 11, 2016 08:07 AM EST

Can marijuana change your brain? Not only may that be the case, but the changes could vary by age. Scientists have found the age at which an adolescent begins using the drug may affect typical brain development.

In this latest study, the researchers analyzed MRI scans ok 42 heavy marijuana users. About 20 participants were categorized as early onset users with a mean age of 13.8, and 22 were labeled as late onset users with a mean age of 16.9. According to self-reports, all participants began using marijuana during adolescence and continued throughout adulthood, using cannabis at least one time per week.

"Science has shown us that changes in the brain occurring during adolescence are complex," said Francesca Filbey, one of the researchers, in a news release. "Our findings suggest that the timing of cannabis use can result in very disparate patterns of effects. Not only did age of use impact the brain changes but the amount of cannabis used also influenced the extent of altered brain maturation."

In typical adolescent brain development, the brain prunes neurons, which results in reduced cortical thickness and greater grey and white matter contrast. Typical pruning also leads to increased gyrification, which is the addition of wrinkles or folds on the brain's surface. In this latest study, MRI results revealed that the more marijuana early onset users consumed, the greater their cortical thickness, the less grey and white matter contrast, and the less intricate the gyrification as compared to late onset users.

The findings reveal that marijuana may have long-term consequences for adolescents. With that said, a longitudinal study is necessary to establish a causal relationship between brain alterations and marijuana use.

The findings are published in the journal Developmental Cognitive Neuroscience.

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