Marijuana use could increase the risk of testicular cancer, according to a study by the Fred Hutchinson Cancer Research Center out this week. If a man has smoked marijuana on a weekly basis or has been exposed to hashish for an extended period of time, the chances of testicular cancer double compared to someone who has never smoked marijuana

The study found that marijuana could also decrease sperm quality, decrease testosterone levels and cause impotency, since these are similar side effects of testicular cancer.

Men already produce a “cannabinoid-like chemical,” which protects the reproductive system from cancer, but marijuana use could reverse that protective chemical and instead work against the body. The marijuana link is somehow associated with “nonseminoma,” malignant germ cell tumors, and is increasing the risk.

The study has prompted more research as it has open up a bevy of questions, said Stephen Schwartz, a member of the Public Health Sciences Division at the Hutchinson Center.

“What young men should know is that first, we know very little about the long-term health consequences of marijuana smoking, especially heavy marijuana smoking,” Schwartz said in a press release. “So, in the absence of more certain information, a decision to smoke marijuana recreationally means that one is taking a chance on one’s future health.”

The National Cancer Institute estimates almost 8,100 men will be diagnosed with testicular cancer, and 380 will die because of it in 2008.