Association of cannabis use and lung cancer: a retrospective cohort study.

BACKGROUND: Lung cancer is the leading cause of cancer-related mortality globally, largely driven by smoking. This study seeks to determine if heavy cannabis use is associated with an increased risk of cancer of the lung and bronchus.

METHODS: This is a retrospective cohort study utilizing 20 years of deidentified electronic medical record data from 67 tertiary healthcare organizations across the United States. Cohorts included adults (≥18 years) diagnosed with cannabis use disorder and a comparison group without cannabis use disorder. Relative risk for development of new cancer of the lung and/or bronchus was analyzed after propensity score matching between groups based on demographics and risk factors for development of lung cancer (n = 149,632 per group).

RESULTS: After matching, individuals with cannabis use disorder demonstrated a significantly higher risk of developing lung and/or bronchus cancer compared to those without cannabis use disorder (RR 3.87, 95% CI 3.43-4.38). The risk remained elevated after one and five years of follow-up. A specific increased risk was found for all histologic subtypes analyzed, including small cell carcinoma (RR 2.70, 95% CI 1.31-5.58), adenocarcinoma (RR 2.54, 95% CI 1.59-4.08), and squamous cell carcinoma (RR 2.90, 95% CI 1.41-5.95).

CONCLUSION: These findings suggest that heavy cannabis use is significantly associated with an increased risk of lung cancer. Given the rising prevalence of cannabis use, further research is needed to clarify dose-response relationships and the biological mechanisms driving these associations. Clinicians should consider these risks when advising patients about cannabis use.