Marijuana smoking may lower the risk of bladder cancer in men, according to a recent study.

Anil A. Thomas, MD, of Northwest Kaiser Permanente, Sunnybrook Medical Office, Clackamas, Ore., and colleagues analyzed data from 84,170 participants in California Men’s Health Study cohort. Of these, 34,000 (41%) reported marijuana use, 47,092 (57%) reported tobacco use, 22,500 (27%) reported using both, and 23,467 (29%) reported using neither. 

Bladder cancer developed in 279 men over an 11-year follow-up period, Dr. Thomas’ group reported in Urology (2015;85:388-393). Bladder cancer developed in 89 marijuana smokers (0.3%) compared with 190 men (0.4%) who did not report marijuana use.

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After adjusting for age, race or ethnicity, and body mass index, use of marijuana only was associated with a 45% decreased risk of bladder cancer, whereas use of tobacco only was associated with a 52% increased risk. Use of both tobacco and marijuana was associated with a 28% increased of bladder cancer.