As cannabis use becomes more mainstream—now legal for recreation in nearly half of U.S. states—it’s easy to overlook its potential risks.
But a recent study suggests the drug may be doing something unexpected: altering brain connectivity in young adults, especially those at risk of psychosis.
Researchers at McGill University used cutting-edge brain scans to examine individuals aged 16 to 30, some with early signs of psychosis.
Cannabis users in this group had lower synaptic density—the connections between neurons that allow the brain to function properly.
What Are Their Findings?
“Cannabis appears to disrupt the brain’s natural process of refining and pruning synapses,” explains Dr. Romina Mizrahi, a professor of psychiatry at McGill.
This process is essential for healthy brain development.
And that disruption could be linked to social withdrawal and lack of motivation—symptoms that are notoriously difficult to treat.
While not every cannabis user will develop psychosis, the study sheds light on why the risk is higher for some.
Researchers hope this knowledge could pave the way for new treatments.
“By focusing on synaptic density, we may eventually develop therapies that enhance social function and quality of life,” says PhD student Belen Blasco.
With scientists now exploring whether these brain changes can predict psychosis, one thing is clear: cannabis may be more than just a “harmless” high.
