(WKBW/ABC News) More than a third of high school seniors report using marijuana in the past year.
A study of 455 men in the journal "Cancer" finds that those who had smoked marijuana were twice as likely to be diagnosed with the most common form of testicular cancer in young men.
Worse, their tumors tended to be faster-growing and harder to treat.
The National Cancer Institute estimates that more than 8500 men will be diagnosed with testicular cancer this year. About 360 will die from it.
Those who survive may face problems with fertility and sexual function.
How marijuana may affect testicular cancer is unclear. The study's author suspects boys who experiment with marijuana during puberty may be especially at risk.
The study adds to a growing body of research that finds smoking pot can have lasting effects on men's fertility and general health.