A new study suggests that cannabis does effect your sperm, but maybe not in the way you might think.
Men who have smoked marijuana have quite a lot more sperm then guys who never have, according to a new study that came out of Harvard. That conclusion surprised Jorge Chavarro - one of the study's lead authors, who is also associate professor of nutrition and epidemiology at Harvard T.H. Chan School of Public Health.
"These unexpected findings highlight how little we know about the reproductive health effects of marijuana, and in fact of the health effects of marijuana in general," Chavarro said in a press release.
In fact, previous research has suggested that cannabis consumption would have negative impacts on sperm health, causing abnormally low sperm counts. However, Chavarro's study found that only five percent of marijuana consumers had less than 15 million sperm per milliliter of ejaculate, which would put them under normal semen levels. Meanwhile, 12 percent of non-cannabis consumers tested below that threshold for a normal sperm count. So a very small percentage of cannabis consumers have low sperm counts in comparison to non-consumers.
On top of that, the average sperm count of cannabis consumers was much higher than the average for non-consumers. And by no small margin. Men who consumed cannabis had an average of 62.7 million sperm per milliliter of ejaculate. In comparison, non-cannabis consuming men averaged sperm concentrations of 45.4 million per milliliter.
But that doesn't mean aspiring fathers should start smoking cannabis to increase their fertility. Researchers warned that heavy cannabis use could bring sperm levels back down to normal.
"Our findings were contrary to what we initially hypothesized. However, they are consistent with two different interpretations, the first being that low levels of marijuana use could benefit sperm production because of its effect on the endocannabinoid system, which is known to play a role in fertility, but those benefits are lost with higher levels of marijuana consumption," said Feiby Nassan, lead author of the study and a postdoctoral research fellow at the Harvard T.H. Chan School.
Nassan also said that the results may have been skewed by cannabis prohibition.
The study's 662 participants were sourced from couples who had visited the Massachusetts General Hospital Fertility Center between 2000 and 2017. Since marijuana was still illegal in Massachusetts at that time, it's possible that many test subjects under-reported or even lied about their cannabis consumption during the trial.
Moreover, it's possible that the relationship between cannabis and sperm is correlative instead of causative. That means smoking a joint might not boost your sperm count, but having a high sperm count might make you more likely to smoke weed.
"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 behaviors, including smoking marijuana," explained Nassan.
But one thing that seems clear from this study is that you probably don't have to worry too much about cannabis destroying your chances at fatherhood.