Heavy Cannabis Use Was Linked to Thinning of a Brain Region Involved in Decision-Making Over Three Years

At three-year follow-up, heavy cannabis users showed significant cortical thinning in the left lateral orbitofrontal cortex compared to both their own baseline and control subjects. The degree of thinning correlated positively with scores on a cannabis use disorder screening tool, suggesting a dose-response relationship.

Longitudinal study comparing cortical thickness changes from baseline to three-year follow-up in young adults with heavy cannabis use versus controls. Brain imaging measured cortical thickness across multiple regions. Cannabis use severity was assessed using the Cannabis Use Disorders Identification Test.

The orbitofrontal cortex is critical for decision-making, impulse control, and emotional processing. Thinning in this area could help explain why heavy cannabis use is associated with difficulty controlling use and making decisions about continued consumption.

This is one of few longitudinal studies tracking actual brain structural changes in heavy cannabis users over time, rather than just comparing users to non-users at a single point. The finding that changes correlate with use severity strengthens the case for a biological link.

Cannot definitively rule out that pre-existing brain differences led to heavier cannabis use rather than the reverse. Sample sizes were not reported in the abstract. Other substance use and lifestyle factors could contribute to cortical changes.