Recreational marijuana use has been linked to an increased risk of testicular cancer, particularly the more dangerous non-seminoma and mixed germ cell tumor types, according to a new study.

Researchers from the Keck School of Medicine at the University of Southern California found that young men who used marijuana in the past were at a doubled risk of having one of these two types of testicular cancer. These types of testicular cancer are known to have worse prognoses than some other kinds.

"We do not know what marijuana triggers in the testis that may lead to carcinogenesis, although we speculate that it may be acting through the endocannabinoid system -- the cellular network that responds to the active ingredient in marijuana -- since this system has been shown to be important in the formation of sperm," study researcher Victoria Cortessis, MSPH, Ph.D., an assistant professor of preventive medicine at USC, said in a statement.

The CANCER study was conducted in 163 young men who were diagnosed with the testicular germ cell tumor type of testicular cancer between December 1986 and April 1991. The researchers compared their drug use with 292 similar men, who were healthy.

Earlier this year, a government study showed that marijuana use is up among teens, with 23 percent of high-schoolers recently reporting smoking marijuana recently. Comparatively, 19 percent of high-schoolers reported recent cigarette use.

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