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Is Smoking Weed Really Bad for Sperm? Here’s What the Science Says

A new study adds to a growing body of evidence that marijuana seriously impacts sperm health. Here’s what would-be dads need to know.

Leaf shape via freepik; illustration by Anne Meadows

Men who hope to become dads and occasionally smoke marijuana often wonder, does weed affect sperm? Does smoking weed lower your sperm count? If you stop smoking weed will your sperm count increase? But then they forget and go back to watching cartoons. In your Monday morning, stone-sober state, it’s natural to remember the root question of the question: marijuana’s effects on sperm. A growing body of research links excessive marijuana use to male infertility, but a new study suggests that there may be graver risks. Although men who smoke marijuana may be able to conceive with partners, cannabis use may increase their child’s risk of autism. This finding raises important questions for couples trying to become parents. There’s still much to be discovered, but there are real concerns around marijuana’s effect on sperm for prospective fathers, even when dads-to-be use weed in small amounts. 

Does Weed Affect Sperm and Fertility?

The medical consensus is that if a couple is having trouble getting pregnant, they should try the sober life for a few months. (And no, “California Sober” doesn’t count.)

“All we can say is that your swimmers may not be as healthy as they could be if you did not have marijuana in your system,” says Jamin Brahmbhatt, MD, a urologist and sexual health expert at Orlando Health who doesn’t mind using the term “swimmers” in a professional context. “For my male infertility patients, I do recommend stopping marijuana to maximize fertility,” he says. 

Doctors who advise against cannabis for men trying to conceive aren’t just trying to harsh their buzz. Studies have shown that weed had a distinct effect on sperm. Heavy marijuana use lowers sperm counts, decreases sperm motility (basically, their ability to wriggle toward an egg), and increases sperm malformation. That doesn’t mean that weed renders sperm completely useless — generations of teenage pregnancies suggest that’s not the case. But for men who are looking for the best shot with their shot, it’s worth cleaning up one’s act.

If you’re not looking to knock up your partner, good news! Marijuana in small doses can combat erectile dysfunction and boost female libido.

Marijuana’s Effects on Sperm

If this new study is any indication, the effect of weed on sperm may be more impactful than previously thought. “We were surprised to find this significant association between marijuana use in men and changes in this gene that is implicated in autism,” says study co-author Rose Schrott, who was a Ph.D. student at Duke University at the time of the study.

After conducting more research that demonstrated 177 potential genetic changes in the sperm of men who use marijuana, Schrott decided to zero in on specific genes. Using 24 men, 12 users and 12 non-users, animal models, and genome-wide analysis of segments of DNA, she and her colleagues found that when men smoked or ingested marijuana, the Discs-Large Associated Protein 2, or the DLGAP2 gene, underwent notable methylation. This matters because the DLGAP2 gene identified is strongly associated with autism as well as schizophrenia and post-traumatic stress disorder.

“Our initial study was really the first of its kind to look at marijuana use in men and changes to his sperm, so we didn’t necessarily expect to see this gene being implicated. But it was a finding that we felt warranted follow-up given its potential involvement in autism and schizophrenia,” Schrott says. 

Since it is the first study of this kind, the findings are very much prospective and need to be duplicated with a larger sample size before there is any reason for men to panic. “We are only able to report this association present in the sperm of men who use marijuana. So what this means for children, we don’t know,” Schrott admits.

Jordan Tishler, MD, a physician and Harvard-trained Holistic Care expert, believes that if the risks of smoking weed were that significant, we’d see the effects more prominently in society — especially in California and certain parts of Greenwich Village. That’s not to say that cannabis use while trying to conceive is risk-free. But those smaller risks need to be carefully examined through many more studies. 

“There is no evidence that heavy marijuana users have trouble conceiving or have an increased risk of ill children. However, no studies looking for those outcomes have been done to date,” he notes. 

It is tempting to jump to the conclusion that the rise in autism cases could be attributed to the mainstreaming of marijuana, as the domestic production of it has increased tenfold over the past 25 years. Still, it’s important to stress that the current study does not directly link men’s marijuana use to autism in their offspring. Rather, it calls for more research on the matter.

Until then, the largest risk prospective dads run with weed is guilt if something does go wrong during the pregnancy. There may be no way to be certain that cannabis caused the problem. But if parents are going to feel terrible about that for the rest of their child’s life, then they should probably take a break from the weed. When it comes to conception, it’s not exactly worth the risk.