A history of drinking has been linked unexpectedly to greater fertility among men.
The result was a big surprise for scientists who measured the sperm count of more than 600 men from couples attending a fertility clinic.
They expected cannabis to have a detrimental effect on sperm count and fertility. Instead, participants who admitted to having already used cannabis were found to have more sperm than non-users.
A surprising Harvard study!
The authors of the study and other experts have not hesitated to point out that smoking cannabis does not necessarily increase the chances of being a father, but that does not necessarily mean that cannabis use is increasing. the risks of paternity.
There may be a non-causal explanation for this association, such as the effect of the male hormone testosterone on sperm count and risk behaviors such as cannabis use.
Dr. Jorge Chavarro, Principal Investigator at the Harvard TH Chan School "These unexpected results show how little we know about the effects of marijuana on reproductive health and, in fact, on the effects of marijuana in general.
"Our results must be interpreted with caution and they emphasize the need to study the health effects of cannabis use."
Previous research involving experiments on animals or men with a history of drug abuse have suggested that cannabis harms men's reproductive health.
For the new study, the researchers took 1 143 semen samples from 662 men between 2000 and 2017.
On average, men were 36 years old, most were white and had a university education. All belonged to couples seeking help for conception in a fertility clinic.
Participants were asked to complete questionnaires detailing their history of cannabis use.
More than half (55%) of men reported having smoked cannabis at some point. Of these, 44% reported having used drugs in the past and 11% were among current consumers.
Analysis of sperm samples showed that men who had smoked marijuana had average sperm concentrations of 62,7 million sperm per milliliter (million / mL). Those who had never smoked a joint had an average of 45,4 million
spermatozoa / mL.
Only 5% of cannabis users had a sperm count of less than 15 million sperm / mL, threshold of the World Health Organization for "normal" levels, against 12% of men who had never smoked cannabis .
However, increased cannabis use was linked to higher levels of testosterone, a male hormone, among smokers.
In the journal Human Reproduction, the scientists said it was possible that low exposure to cannabis could be beneficial for sperm production in one way or another.
The endocannabinoid chemical messenger system in the brain, which is targeted by the drug, is known to play a regulating role of fertility.
On the other hand, the association may have nothing to do with the effects of cannabis.
Dr. Feiby Nassan, another member of the Harvard team, said, "An equally plausible interpretation is that our findings may reflect the fact that men with higher testosterone levels are more likely to behave differently. at risk, including smoking grass. "
Allan Pacey, Professor of Andrology at the University of Sheffield, echoed this view.
"As the authors point out, men whose sperm concentration is higher are likely to have more testosterone in their body and therefore be more likely to smoke cannabis because they are simply willing to take more risks. In conclusion, I am not convinced that this document will move us forward in this debate. "Moreover, it does not support the apparent benefits of fertility consumption either.
Two different interpretations: the first being that low levels of cannabis use could be beneficial for sperm production because of its effect on the endocannabinoid system, which is known to play a role in fertility, but these benefits are lost when Cannabis use increases "