Smoking pot could damage your semen quality, or so suggests a new study out of Denmark. Some 1,215 Danish men ages 18 to 28 were asked about their drug use over the past three months and provided a semen sample.
The researchers found a correlation between men who smoked pot more than once weekly and "quite a lot" of a drop in sperm count: the count was an average 29% lower in these men than in those who reported lighter or no usage.
Those who reported additional drug use (anything from cocaine to ecstasy) saw an even more severe reduction, with average sperm count down 55%. "Our findings are of public interest as marijuana use is common"—indeed, 45% of participants had smoked in the last 3 months—"and may be contributing to recent reports of poor semen quality," the University of Copenhagen researchers write in the American Journal of Epidemiology.
There could be two things going on, they tell Live Science. It's possible the interaction between THC and receptors in the testes causes the drop.
Or it might not be the marijuana at all. "We cannot exclude the possibility that the men who used marijuana generally have an unhealthier lifestyle and health behavior, which may also affect their semen quality and hormone levels," say the researchers.
They did, however take into account caffeine, alcohol, and cigarette consumption, and the tie still held. A 2014 study found that pot usage was strongly associated with "abnormal sperm morphology.