That study saying pot makes sperm swim better? Here’s why it’s questionable

In February, Harvard University blew up the internet with the apparent revelation that, rather than killing sperm, cannabis actually made it better.

But the finding, soon circulated around the world, left out one critical detail: Harvard scientists had only looked at men who were already having fertility problems.

 

 

The paper, published in the journal Human Reproduction, examined 1,143 sperm samples from 662 men and came to the somewhat conclusion that men who had ever smoked marijuana had higher sperm concentration … than men who had never smoked marijuana.”

But it wasn’t a random sample of 662 men. All of the men were recruited for the study at the Massachusetts General Hospital Fertility Center, where they were all being treated for “sub-fertility”; basically, an inability to conceive.

In other words, the pot smokers did indeed have better sperm than the pot abstainers, but both groups nevertheless have bad semen that doesn’t work right.

“Our results may not (be) generalizable to men in the general population because men in the current study were enrolled from a fertility centre,” it reads.

The findings are still surprising: Harvard researchers had expected that the pot smokers would be more sub-fertile, not less. But given that all of the 662 men are still having fertility problems, it’s not exactly a sterling endorsement of cannabis as a fertility drug.

The study authors also found that even among though past use of marijuana was correlated with better sperm, a man’s sperm sample would be healthier the longer he had spent without smoking a joint.

“These other results raise the possibility that our findings are not explained by a true underlying biologic mechanism but are instead spurious associations,” reads the report.

Meanwhile, among studies have tested the effects of cannabis on otherwise healthy men, the opposite conclusion has been reached. A 2015 study tested the sperm of 1,215 Danes and found that among the weed enthusiasts, sperm count could be up to 52 per cent lower than the weed-abstainers.

In sum, all that really came out of Harvard last month was the revelation that pot may not be as bad for sperm as previously thought, and that it’s still plausible that low doses of the drug might be helpful.

However, even that might simply be a coincidence.

“An equally plausible interpretation is that our findings could reflect the fact that men with higher testosterone levels are more likely to engage in risk-seeking behaviours, including smoking marijuana,” Feiby Nassan, lead author of the Harvard study, said in a press release.

• Twitter: TristinHopper | Email: [email protected]

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