Harvard study shows men who smoke cannabis have higher sperm counts

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Researchers at Harvard University found that cannabis could affect a man’s fertility, but not in the way you might think.

The surprising results from the research found that men who regularly smoke cannabis have higher sperm counts than men who don’t smoke. The findings were published in the journal Human Reproduction earlier this week and have received worldwide attention since previously it was thought that cannabis consumption will negatively affect a man’s sperm count.

The researchers tested 662 men enrolled at the Massachusetts General Hospital Fertility Center between 2000 and 2017. From these men, they collected 1,143 semen samples. Of the 662 men, 365 reported having smoked marijuana and these men are reported to have had “significantly higher sperm concentration”. They are said to have had 63 million sperm per milliliter of semen whereas the 297 men who reported never smoking cannabis only had 45 million per milliliter.

The researchers appropriately adjusted findings for other factors including abstinence time, smoking, coffee consumption, age, alcohol and cocaine which can all affect sperm counts. They also found that the sperm counts did not differ very much when comparing current and former cannabis smokers.

“These unexpected findings from our study highlight that we know too little about the reproductive health effects of cannabis and, in fact, of the health effects in general, to make strong statements about the impact of cannabis and, in fact, of the health effects in general, to make strong statements about the impact of cannabis on health, with the possible exception of mental health,” said Jorge Chavaro, lead researcher and associate professor of nutrition and epidemiology at Harvard.

The research also found that men who smoke more often within the group that had ever smoked cannabis had higher testosterone levels.

“An equally plausible interpretation is that our findings could reflect the fact that men with higher testosterone level are more likely to engage in risk-seeking behaviors, including smoking marijuana,” said Feiby Nassan, an environmental health and nutrition researcher at Harvard.

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.

“An equally important limitation is the fact that most of the data were collected while cannabis was illegal in Massachusetts, so it is difficult to know to what extent men may have under-reported use of cannabis because of social stigma or potential consequences related to insurance coverage for infertility services,” said Dr. Nassan.

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

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