Study links early cannabis use to earlier onset of psychosis

A major Australian-led global study published in Biological Psychiatry has linked early cannabis use to a higher risk of mental illness and an earlier onset of psychosis. The research, which analyzed data from over 70,000 individuals across 149 studies, found that cannabis users develop psychosis an average of two and a half years earlier than non-users who experience the condition.

The study highlighted that younger users face worse clinical outcomes. Specifically, those in their early 20s developed psychosis 1.6 years earlier than non-users, while those over 30 saw an onset approximately 6.3 years earlier. Researchers noted that the risk appears tied to cumulative toxicity and years of exposure, comparing the long-term impact to that of tobacco and lung cancer.

Co-authors Matthew Large, a professor of psychiatry at the University of NSW, and Carly Stevens, noted that the findings challenge the misconception that waiting until the mid-20s to use cannabis mitigates these risks.