Marijuana use may increase a man’s risk of testicular cancer, particularly the nonseminona or mixed-histology form, according to a study published in Cancer (2009;115:1215-1223).

Janet R. Daling, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, and her colleagues compared 369 men with testicular germ cell tumors and 979 age-matched controls. The researchers found that 26% of testicular cancer patients reported current marijuana use versus 20% of controls.

Compared with men who never smoked marijuana, current smokers had 70% increased risk of testicular cancer, a 30% increased risk of pure seminoma tumors, and 2.3 times increased risk of nonseminoma or mixed-histology tumors, after adjusting for potential confounders. Former marijuana smokers had a 20% increased risk of all types of testicular tumors.

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In addition, the risk of testicular cancer increased by 40% in men who smoked marijuana less than once per week and by twofold in those who smoked marijuana at least a week, investigators reported.