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

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