Cannabis use linked to nearly 4x higher lung cancer risk

This retrospective cohort study analyzed 20 years of medical records from over 300,000 patients across 67 U.S. healthcare organizations to examine whether heavy cannabis use increases lung cancer risk. Researchers compared 149,632 individuals with cannabis use disorder to a matched comparison group without cannabis use disorder, controlling for smoking status and other risk factors. The findings were striking: people with cannabis use disorder showed a 3.87-fold increased risk of developing lung or bronchus cancer compared to those without cannabis use disorder, with risks remaining elevated at both one and five-year follow-ups.

The elevated risk appeared across all lung cancer types examined, including small cell carcinoma (2.70-fold increase), adenocarcinoma (2.54-fold increase), and squamous cell carcinoma (2.90-fold increase). This consistency across different cancer subtypes suggests a robust association rather than a chance finding. The study controlled for traditional risk factors like smoking history, meaning the increased risk was observed even after accounting for potential confounding factors that might explain the association.

Given the growing legalization and use of cannabis in many regions, these findings carry important public health implications. The researchers emphasize that further investigation is needed to understand dose-response relationships and the biological mechanisms linking cannabis use to lung cancer risk. Clinicians are advised to discuss these potential risks with patients considering cannabis use, particularly heavy or long-term use patterns. The study highlights a critical gap in our understanding of cannabis's health effects and underscores the importance of continued research as cannabis use becomes more common.