Published: Thu, February 07, 2019
Medicine | By Brett Sutton

Smoking cannabis linked to higher sperm counts in surprising study

Smoking cannabis linked to higher sperm counts in surprising study

In December 2018, INSIDER reported on a small study from Duke University that suggested marijuana use could be linked to lower sperm concentrations, a factor that can affect a man's fertility.

In the latest study, published Tuesday in Human Reproduction, researchers at the Harvard T.H. Chan School of Public Health and elsewhere looked at a specific group of men: fertility clinic patients.

As reported by the Bloomberg, the investigators collected over 1,143 semen samples from 662 men who had sought for contraception help at the health facility between 2000 and 2017.

A U.S. study of men seeking fertility treatment found that those who had smoked marijuana had a higher sperm concentration than those who never used the drug.

To the researchers' surprise, though, the cannabis users had noticeably higher sperm counts on average (62.7 million sperm per milliliter of semen) than did the men who said the never used cannabis (45.4 million sperm per milliliter of semen).

They reckoned that there could be a "non-casual explanation" to the effect of male testosterone on "sperm count and risk-taking behaviours".

The marijuana users were smoking relatively modest amounts of marijuana, two to three joints per week, on average.

Chavarro warned that the findings don't necessarily mean that smoking pot increases the chances of making a baby.

USA lead researcher Dr Jorge Chavarro said: "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".


However, Chavarro noted that some of those past studies surveyed men who use multiple drugs at once, making it hard to pinpoint the effects of marijuana alone. The researchers also studied blood samples provided by 317 men, in order to quantify the levels of reproductive hormones.

Given the illegal status of marijuana in some places and its social stigma, the researchers also have reason to believe some of the participants they studied underreported their marijuana use in the surveys.

The men were, on average, 36 years old, mostly white and mostly university-educated.

On the other hand the association could have nothing to do with the effects of cannabis.

"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 drug use".

Feiby Nassan, lead author of the study and a postdoctoral research fellow at Harvard Chan School, told Newsweek: "Because the endocannabinoid receptors (the ones responsive to marijuana) are found in many places in the body especially the reproductive system, we need to understand their role on our health, especially with increasing their legalization".

Scientists analysed the sperm quality of regular cannabis smokers as well as non-smokers, with some unexpected results.

Chavarro also went on to point out that if the study proves anything definitive, it is that the link between marijuana and general health remains something of a grey area. But maybe men with high testosterone are just more likely to do drugs.

'In my opinion, this should be avoided at all costs in any couples trying to start a family'.

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