Study Finds Cannabis Might Not Lower Sperm Count After All

Grant Boone
February 7, 2019

A bunch of scientists gathered sperm counts from 662 men who visited a fertility clinic with their significant other and they were shocked to find that participants who took marijuana at some point in their life have higher sperm count than others.

The findings are "not consistent" with previous research, which has suggested that marijuana has a harmful effect on men's testicular function, the researchers said. The research is published in the journal Human Reproduction.

Lead researcher Dr Jorge Chavarro, from the Harvard TH Chan School of Public Health in Boston, 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. Many people assume this means the drug is totally safe to use, but scientists are still working out exactly what it does to our bodies. For example, in 2015, researchers from Denmark found that men who smoked marijuana a couple of times per week had sperm counts that were almost 30 percent lower than those who didn't smoke marijuana, or those who used the drug less frequently.

Out of those who reported to have been using bhang, only 5% had sperm counts below 15 million/ml, the threshold for normal levels as per the World Health Organisation.

However, some researchers say that men with naturally higher testosterone levels are more likely to engage in risk-taking behaviours - meaning they are more likely to have tried cannabis.

Fifty-five percent of the men said they had smoked marijuana at some point, with 44 percent doing so in the past and 11 percent being current users. However, the new study showed that men who smoked weed had an average sperm concentration of 62.7 million sperm per millilitre (million/mL). That's a lot. It's also possible that, as some research has suggested, heavy or early cannabis use is really what can harm sperm, while the occasional puff as an adult might provide a boost to fertility.

Nevertheless, the study authors quickly noted that smoking cannabis may not mean that one's chances of becoming a father increases.

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Prior work has identified many sex differences in the brain, including during brain aging and in neurodegenerative diseases. The study was recently posted in the journal Proceedings of the National Academy of Sciences of the United States.

"Our results need to be interpreted with caution and they highlight the need to further study the health effects of marijuana use".

Researchers analysed health surveys from men who sought fertility treatment at the Massachusetts General Hospital Fertility Center between 2000 and 2017.

For now, there's just not enough evidence to make any conclusions about the use of marijuana on male sperm.

In addition, it takes about three months for men to undergo a full cycle of sperm production to produce mature sperm.

And yet, the study still found that men who said they used marijuana at least a year ago had higher sperm counts than men who used it more recently. Vij said she wondered if "there's something that goes along with marijuana use" that's tied to better sperm production.

One widely circulated 2014 study involving almost 2,000 British men - the world's largest study to explore how common lifestyle factors influence sperm morphology (the size and shape of sperm) - found that males under 30 with less than four-per-cent normal sperm were almost twice as likely to have used cannabis in the previous three months.

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