Heavy Cannabis, Light Tobacco Co-Use Raises Psychosis Risk 2.93-Fold in 734 High-Risk People
Updated
Updated · Nature.com · May 12
Heavy Cannabis, Light Tobacco Co-Use Raises Psychosis Risk 2.93-Fold in 734 High-Risk People
3 articles · Updated · Nature.com · May 12
A North American study of 734 people at clinical high risk for psychosis found heavy cannabis use combined with light tobacco use was linked to the highest conversion risk, with a hazard ratio of 2.93 versus no use.
Across 1,012 participants, more frequent cannabis and tobacco use each tracked with worse psychosis, anxiety and depression symptoms, but co-use itself did not produce more severe baseline symptoms than single-substance use within the high-risk group.
Cannabis use alone also predicted higher conversion risk in age- and sex-adjusted analysis, with a hazard ratio of 1.17, while tobacco use alone was not significantly associated with conversion.
The findings come from NAPLS2 data collected in 2009-2013 across eight North American sites, and the authors said newer studies are needed because cannabis potency, legalization and vaping have changed since then.
Can quitting reverse the tripled psychosis risk for teens who mix cannabis and tobacco?
Beyond psychosis, what silent heart and brain damage comes from mixing cannabis and tobacco?
Co-Use of Cannabis and Tobacco Triples Psychosis Risk in Vulnerable Youth: New Study Warns of Urgent Public Health Threat
Overview
A major multisite study led by Dr. Heather Ward, published in Nature Mental Health, has advanced our understanding of psychosis risk by showing that high-risk youth who co-use cannabis and tobacco face nearly three times the risk of developing psychosis compared to non-users. The research highlights that heavy cannabis use combined with light tobacco use is especially dangerous, making the long-term risk of severe psychotic illness much higher. These findings stress the urgent need for early intervention and targeted prevention to protect vulnerable individuals and improve their long-term mental health outcomes.