If you’re a testicle-having person who smokes weed, you’ve probably heard that you’re harming your reproductive health. You’ve probably heard that smoking weed lowers your sperm count or reduces the quality or DNA integrity of your sperm. If you’re not trying to have a kid, maybe that sounds just fine. But a new study by Harvard medical researchers, published today in the journal Human Reproduction, is challenging this oft-repeated conventional wisdom. According to researchers, smoking weed may actually make a person’s testicles more fertile, not less.
Men Who Had Ever Smoked Weed Had Significantly Higher Sperm Count, Study Finds
The idea that consuming marijuana lowers sperm count may not just be wrong, but the exact opposite of the truth. That’s according to a new peer-reviewed article, “Marijuana smoking and markers of testicular function among men from a fertility centre.” Researchers say that smoking weed—at all, ever—could increase not only sperm count but also sperm concentration in semen. In short, smoking weed may increases male reproductive fertility, not reduce it.
The conclusion flies in the face of what people have said and thought about cannabis and fertility for years. And no wonder. Newspapers, magazines and websites (even birthcontrol.com!) have published articles on the negative impacts of marijuana on male fertility. And to be fair, most of those articles are based on scientific studies which suggests weed isn’t doing anyone’s sperm any favors.
But a closer look at those studies presents a much more complex picture. We still know relatively little about the human endocannabinoid system (ECS), let alone how it interacts with other bodily systems. And studies that have looked into links between the ECS and the endocrine system have yet to produce definitive or conclusive data about the effects of cannabis on fertility.
The same is of course true about this new Harvard study. But its conclusions suggest we may have everything backward when it comes to what we think weed does to sperm.
18-Year Study Could Reverse Everything We Think We Know About Marijuana and Fertility
Between 2000 and 2017, Harvard researchers conducted a study of 662 subfertile males enrolled at the Massachusetts General Hospital Fertility Center. Over that time, the study participants produced a total of 1143 semen samples. Roughly half of the participants also provided blood samples, allowing researchers to measure their reproductive hormone concentrations.
Participants self-reported cannabis and other drug use, so that data point isn’t perfect. However, 365 of them reported that they had smoked marijuana at some point. The rest said they had never smoked weed. And according to researchers, those 365 participants “had significantly higher sperm concentration than men who had never smoke marijuana.” In quantitative terms, that means 62.7 million/mL for weed smokers compared to 45.4 million/mL for non.
Furthermore, researchers found similar results when they measured for total sperm count, challenging the idea that marijuana smokers produce less semen. Interestingly, researches said it made no difference whether the participant was a current or past marijuana smoker, challenging the idea that cannabis has just a temporary or reversible effect on male fertility.
Also interesting was the data showing that marijuana smokers came up shorter than non-cannabis consumers in one category: follicle stimulating hormone (FHS). FSH is the hormone that promotes the formation of ova or sperm. And the study found that cannabis smokers had significantly lower FSH concentrations than never smokers.
Researchers aren’t sure why cannabis smokers in the study had lower FSH but higher sperm concentration and count. They also didn’t observe any impact of cannabis consumption or not on other semen parameters like DNA integrity.
Researchers Call for Further Studies on Cannabis and Reproductive Health
The new Harvard study only suggests that smoking weed is associated with higher sperm count. And researchers are still open to the possibility that there’s a completely weed-free explanation to the data they obtained. One hypothesis suggests that since consuming cannabis is “risky behavior,” it may increase testosterone levels, leading to higher sperm counts. Whatever the relationship is between weed and male fertility, don’t count on it lowering your sperm count.