What Does Marijuana Really Do to Sperm?

September 17th 2015

Smoking pot might lower your sperm count by up to roughly one-third, according to a study published in the American Journal of Epidemiology. Researchers at the University of Copenhagen surveyed 1,215 Danish men between the ages of 18 and 28, finding that those who reported using marijuana more than once a week had "quite a lot" less sperm than non-users.

But before all of you male stoners freak out, there are a few things to keep in mind here. First, even though a 28 percent sperm count reduction might seem like a serious semen problem, it does not necessarily mean that chronic smokers are at risk of infertility. The average count is 39 sperm per milliliter, and anything below 15 million sperm per milliliter is considered low. Now if you do that math, having one third less than the average sperm count still leaves you with about 28 million sperm per milliliters—still falling in the "average" zone—depending on the size of a man's testes.

Second, even the researchers conceded that they could not definitively attribute marijuana use to reduced sperm counts. The way they went about this research involved looking at the results of compulsory medical examinations that male recruits had to take in order to join the Danish military. They had to submit sperm samples that were then analyzed by the researchers, and 45 percent of those recruits reported using marijuana in the past three months.

"Our findings are of public interest as marijuana use is common and may be contributing to recent reports of poor semen quality," the researchers wrote in the study. However, they added, "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."

Unflattering as that may sound for regular users, it is an important distinction to keep in mind. For participants who reported using marijuana as well as other recreational drugs (e.g. cocaine and ecstasy), the sperm count reduction averaged 55 percent—almost double that found in the pot-only group.

That said, this is not the first study to suggest that marijuana might have a negative impact on sperm. A 2014 study published in the journal Human Reproduction found that, of all the substances they included in their research on sperm morphology, marijuana use had the most pronounced effect on the shape of sperm cells.

"I do know there is some work in laboratory animals that suggests [marijuana] can affect the way the DNA in the sperm is packaged together, and that’s significant," Dr. Alan Pacey, lead author of the study, told Fox News. "When sperm are made, the DNA they maintain has to be packaged in the head very tightly, and when that process doesn’t work properly, you get an abnormal sperm. So the cannabis is maybe interrupting that DNA folding."

But despite the fact that his research yielded these results, Pacey added that he was not particularly convinced that any one substance can be blamed for reproductive issues such as male fertility, arguing that the most powerful influencer in that respect is simply genetics. He still recommended abstaining from marijuana use for at least three months—the time it takes to produce sperm—if you are trying to have a baby with your partner, but as far as the long-term effects are concerned, more research is needed.

"There are fewer risks than people think, and that makes sense to me," Pacey concluded. "The single thing that affects fertility is how big your testicles are. If you're blessed with big testicles, you'll produce more sperm."

On a related note, if you're not trying to have a baby but still want to have good sex, maybe getting stoned really is the best thing for you; science has found that marijuana increases sex drive, as ATTN: has previously reported.

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