As cannabis use rises with growing legalization and acceptance, new research highlights serious concerns about its impact on brain health. A McGill University study published in JAMA Psychiatry found that cannabis use can reduce brain connectivity and increase the risk of psychosis, especially in young adults already vulnerable to mental health issues.

Using brain scans, researchers found lower synaptic density—vital for communication between neurons—in individuals at risk for psychosis. Cannabis use worsened this reduction, likely by disrupting the brain’s natural synaptic pruning process, which is essential for healthy development.

The study also identified damage in key brain areas tied to memory, decision-making, and emotion, especially in long-term or heavy users. A related study in JAMA Network Open confirmed these findings, showing reduced brain activity in users performing memory tasks.

These findings suggest cannabis can amplify existing risks for psychosis and harm cognitive functions. As use becomes more widespread, researchers emphasize the need for balanced public awareness of both the benefits and risks of cannabis.