Men who smoke weed, especially young men, could develop fertility problems as a result, a British study found.
The study, authored by Dr. Allan Pacey, senior lecturer in andrology at the University of Sheffield in Great Britain, was published in the journal Human Reproduction. Researchers analyzed and compared the sperm of 1,970 men.
About 16 percent of the subjects, 318 men, produced what researchers classified as abnormal sperm. That means less than 4 percent of their sperm was the correct shape and size, according to standards from the World Health Organization.
“Cannabis smoking was more common in those men who had sperm morphology less than 4 percent,” Pacey said. “Cannabis affects one of the processes involved in determining size and shape. And we also know that the way cannabis is metabolized is different in fertile and infertile men.”
Weed an Important Factor in Sperm Health
Researchers found that the men with abnormal sperm were typically younger than 30, had used pot within three months prior to giving their semen sample, and were more likely to have been tested during the summer.
Sperm shape and size could be affected by any of those factors, or others, the scientists acknowledged. The study didn’t attempt to dig much deeper or verify any of the facts participants provided about their lives – so the real extent of pot use and other important details may be uncertain.
But the researchers did rule out a number of other factors, saying they had no apparent effect on male fertility. Those included cigarette smoking, alcohol consumption, use of other recreational drugs, work history, body mass index, medical history, and the type of underwear worn by each man.
Experts: No Weed if You’re Trying to Conceive
The American Society for Reproductive Medicine officially recommends against marijuana use by men trying to conceive, saying it’s tied to impaired sperm function. The drug has long been linked to fertility issues, though in many cases the evidence has been hyped beyond its limits.
For one thing, doctors simply recommend that men seeking to conceive stop toking. There is no evidence suggesting sperm defects caused by cannabis are permanent. And other commonly consumed substances, including caffeine, are known to cause infertility in men or women.
What’s more, experts admit they don’t have enough information to draw any definite conclusion about weed and fertility. The evidence is persuasive, they say, but not conclusive.
“The take-home lesson of the article is that clinicians should counsel their patients on the possible relationships between lifestyle factors, abnormal semen parameters, and fertility outcomes,” said Rebecca Sokol, president of the Society for Reproductive Medicine. “This should include a discussion that the data are often inconclusive, but the motto ‘everything in moderation’ is a wise approach for the couple who is planning a pregnancy.”