The perception of cannabis as a relatively benign substance may need serious reconsideration as mounting evidence connects heavy use to serious respiratory consequences. A comprehensive analysis of nearly 300,000 medical records spanning two decades reveals that individuals with cannabis use disorder face nearly four times the risk of developing lung cancer compared to non-users, with elevated risks persisting across all major cancer subtypes.
The retrospective cohort study examined electronic health records from 67 major healthcare organizations, comparing 149,632 adults with cannabis use disorder to an equal number of matched controls. After accounting for demographics and traditional lung cancer risk factors, cannabis users showed a relative risk of 3.87 for developing lung or bronchial cancers. The increased risk affected all histologic subtypes: small cell carcinoma (2.70-fold increase), adenocarcinoma (2.54-fold), and squamous cell carcinoma (2.90-fold). Risk elevation remained significant at both one and five-year follow-up periods.
These findings challenge assumptions about cannabis safety, particularly as legalization expands access and social acceptance grows. The magnitude of risk approaches that seen with tobacco smoking, suggesting cannabis combustion products may be similarly carcinogenic. However, important limitations temper these conclusions: the study relies on diagnoses of cannabis use disorder, representing the most severe use patterns, and cannot distinguish between smoking methods, dosing, or concurrent tobacco use. The observational design also cannot establish definitive causation. Nevertheless, this represents the largest longitudinal analysis to date connecting cannabis use to lung cancer, warranting serious consideration for both clinical practice and public health policy.