Marijuana May Not Hurt Sperm Counts Finds A Surprising Study

Kenny Tucker
February 10, 2019

"There are men in the world who have never smoked a joint in their life and they have lots of children and there are others who smoke every day and never got their partner pregnant", said Morrison.

"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", said Harvard professor Jorge Chavarro.

And rightfully so. In 2015, a study published in the American Journal of Epidemiology examined 1,215 healthy young men and found that those who used recreational marijuana a couple of times per week had lower sperm counts than those who used the substance less often or not at all.

Fifty-five percent of the men said they'd smoked pot at some point, with 44 percent saying they were past smokers and 11 percent reporting they now toke.

The first author of the study, Dr Feiby Nassan, a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health, said: "Our findings were contrary to what we hypothesised at the start of the study".

"We spent a good two months redoing everything, making sure that there wasn't any error in the data", Cahvarro was quoted by Bloomberg.

The surprising results from the research found that men who regularly smoke cannabis have higher sperm counts than men who don't smoke.

The researchers expected that smoking cannabis would be associated with worse semen quality, as historical studies had suggested the drug has negative effects on reproductive health.

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A 2015 study also done at the UWI suggested that chronic marijuana use negatively affects sperm quality.

Of all those who participated, 55 percent had smoked marijuana before - 44 percent of those men had tried it in the past, while 11 percent were current marijuana smokers. They believe that some might have underreported their habits considering that marijuana was illegal for most of the study period.

"With increasing use of marijuana, there was a positive association with serum testosterone levels", Chavarro said. But wait, there's more: Only 5% of marijuana smokers had sperm concentrations below that normal threshold, compared to 12% of never-smokers.

All of the men answered questions about their marijuana use, and about half also provided blood samples that were analyzed for reproductive hormone levels.

One possible explanation could be that men who generally produce higher testosterone levels are more likely to use marijuana, rather than the implication that cannabis use itself affects sperm potency.

"It is important to understand that the difference in sperm concentration between light smokers and never-smokers is not necessarily associated with a difference in fertility potential", Kawwass said. The findings held even after the researchers took into account some factors that could have affected sperm concentration, such as age, cigarette smoking and alcohol use.

Nassan also made a point of acknowledging that there were limitations when conducting the study and that the findings may not be totally accurate as many people may not have admitted to smoking cannabis.

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. Another reason, according to the researchers, is that men may be more likely to engage in "risk-seeing activities", like smoking marijuana, if they have higher testosterone concentrations- something that aids in fertility.

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