According to ABC News:
The study of 455 Californian men found those who had smoked pot were twice as likely to have been diagnosed with testicular germ cell tumors, the most common form of testicular cancer in men younger than 35.
“Testicular cancer is on the rise,” said study author Victoria Cortessis, assistant professor of preventive medicine at the University of Southern California's Keck School of Medicine in Los Angeles. “So we asked, 'What is it that young men are doing more frequently that could account for the increased risk?'”
“We now have three studies connecting marijuana use to testicular cancer, and no studies that contradict them,” said Stephen Schwartz, an epidemiologist at the Fred Hutchinson Cancer Center in Seattle and author of the first study linking marijuana use to testicular cancer in 2009. “I think we should start taking notice.”
But other factors could be at play, as men who use marijuana are more likely to drink and use other drugs. However, Cortessis found men who used cocaine were actually less likely to develop testicular cancer – a result that might reflect the drug's toxic effects.
“My suspicion is that the effect of cocaine is to kill the germ cells so they're not there,” she said, describing how cocaine cuts testicular size and function in mice. “It's more analogous to a mastectomy to reduce the risk of breast cancer. And for a young guy, that would be high price to pay.”
If it wasn't for the whole part about snorting coke to reverse the ill effects of smoking pot, I'd have said this study was likely put out by Johnny Law as an attempt at fear mongering and suggest that no one take any of this at face value. Now I don't know what the f*ck to tell you other than: if you ignore this warning you might be bringing your empty scrotum to a taxidermist someday. So your call.