LOS ANGELES, Sept. 11 (UPI) -- Recreational marijuana use was linked to an increased risk of subtypes of testicular cancer that tend to carry a worse prognosis, U.S. researchers say.

Victoria Cortessis, assistant professor of preventive medicine at the Keck School of Medicine of the University of Southern California in Los Angeles, and colleagues looked at the self-reported history of recreational drug use in 163 young men diagnosed with testicular cancer and compared it with that of 292 healthy men of the same age and race/ethnicity.


Researchers suspect the increase in this type of cancer -- most often diagnosed in men ages

15-45 is due to increasing exposure to unrecognized environmental causes, Cortessis said.

The study, published online ahead of the print edition of the journal Cancer, found men with a history of using marijuana were twice as likely to have subtypes of testicular cancer called non-seminoma and mixed germ cell tumors. These tumors usually occur in younger men and carry a somewhat worse prognosis than the seminoma subtype.

"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," Cortessis said in a statement.