Grey Matter Volume Differences Associated with Extremely Low Levels of Cannabis Use in Adolescence

The Journal of Neuroscience

This research article shows that teenagers who have only used cannabis once or twice in their lifetime have brain differences compared to teenagers who have never used cannabis.

More specifically, low-level cannabis users had slightly more grey matter in brain regions that include the amygdala, hippocampus, striatum, and the left prefrontal cortex. The researchers also found that greater grey matter in one of the brain regions was associated with decreased performance on a perceptual reasoning task. However, this had no association with a verbal comprehension task. Grey matter differences in other regions were not associated with performance on either of the two tasks.

It remains unclear how to interpret these findings of greater brain volume. Studies on adult populations with heavy cannabis use tend to show lesser brain volume.

While most researchers focus on heavy cannabis use, only a few studies have investigated what happens to the brain after the first few uses. The study was part of a long-term European project known as IMAGEN. This study included 46 participants that were 14 years of age and reported only one or two instances of lifetime cannabis use. They were compared to 69 participants with similar demographics, but who had never used cannabis. The longitudinal design of the IMAGEN study (where they measure behavior and brain anatomy over time) allowed the authors to rule out the possibility that these differences were present before the first use of cannabis.

For the original article, click here.

Orr, C. et al. (2019). Grey Matter Volume Differences Associated with Extremely Low Levels of Cannabis Use in Adolescence. Journal of Neuroscience, Volume 39 (Issue 10), pp. 1817-1827. DOI: https://doi.org/10.1523/JNEUROSCI.3375-17.2018