The use of marijuana in young adulthood might increase the risk of testicular cancer, researchers at the University of Southern California said in a study published by the medical journal Cancer on Monday.

No tests were carried out to determine whether marijuana use actually causes cancerous growths, but the study marks the first scientific research to actually spot a correlation between marijuana use and testicular cancer.

Researchers said that after interviewing more than 350 men, including a focus group of 163 who were diagnosed with testicular cancer, they determined that men who smoked marijuana in their adolescence and later quit "had a 2-fold increased risk" for developing dangerous germ cell tumors.

While that increase is statistically significant, it amounts to a relatively small number for the population at large. "[It's] safe to say that lifetime risk of testis cancer is less than 1 [percent] overall, presumably this was doubled among those who used marijuana," the study's author, University of Southern California Assistant Professor Victoria Cortessis, told Raw Story.

Professor Paul Pharoah at Cambridge lowballed the increase even further, telling Australian academic journal The Conversation that men in their 20s who use marijuana increase their risk of testicular cancer by about 0.012 percent.

The study's results also showed, oddly, that men who reported using marijuana frequently did not have a statistically significant increase in their risk of developing testicular cancer. Bizarrely, men who used cocaine actually reduced their risk, which led researchers to speculate that cocaine use may make testicular cancer less likely by reducing fertility.

The National Cancer Institute estimates that out of more than 151.7 million men living in the U.S. today, 8,590 will be diagnosed with testicular cancer in 2012, and 360 of them will likely die.


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