Use of marijuana may increase the risk of testicular cancer, according to a study presented at the Annual Meeting of the American Association for Cancer Research.

For the study, Britton Trabert, PhD, of the National Cancer Institute, and colleagues conducted a case-control study and identified 187 cases of germ-cell tumors in men 15 to 50 years old at the time of diagnosis. Participants completed a self-administered questionnaire, which included items related to environmental exposures and history of drug use. When responses were categorized by frequency of marijuana use, daily or more than once daily was reported by 7.1% of the control group and 18.5% of the patients.

Results of the study revealed that daily marijuana use tripled the risk of germ-cell cancer, and use for more than 10 years doubled the risk. Furthermore, when frequency and duration of marijuana use among patients were examined according to tumor type, researchers found that a significantly higher proportion of patients with nonseminoma tumors reported daily or more than once-daily marijuana use compared with the control group, 22.3% compared to 7.1%, respectively.

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“We can only speculate about the nature of this association, but one possibility is that exposure to marijuana during puberty might play a role in the development of nonseminoma, which occurs about a decade earlier than seminoma,” noted Dr. Trabert.

According to the press release announcing the findings, testicular germ-cell tumors account for fewer than 2% of male cancers, but they are the most common form of cancer in younger men 15 to 44 years old.