Cannabis: Sperm count and testosterone could increase after use

Henrietta Strickland
February 7, 2019

All the men were seeking treatment at the Massachusetts General Hospital Fertility Center.

Previous studies have linked heavy cannabis use to lower testosterone levels and a decline in both sperm production and quality.

Men who smoke marijuana may have higher sperm counts than those who have never used the drug, a surprising new study finds.

And this difference in physiology or other associated behaviours might then also be responsible for the difference in sperm counts, rather than the marijuana. Male cannabis users were also less likely to have unhealthy sperm counts than teetotalers. This finding, which contradicts past research on the topic, shocked the researchers.

"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", says co-author Jorge Chavarro, an expert in nutrition and epidemiology at Harvard University. "We were very, very surprised about this".

Dr. Feiby Nassan, one of the authors of the study, said men with higher testosterone levels are more likely to engage in risky behavior, like drug use, which could be behind the study's finding of higher sperm counts.

He said studies in the past that suggest drug use lowers sperm count don't specify cannabis, and are usually an amalgamation of several drugs.

Researchers collected 1,143 samples from 662 men between 2000 and 2017. They also asked the men about past and present marijuana use, though they did not ask about specific dosages or frequency.

In total, 55 percent of the men admitted to trying cannabis at some point in their lives, while 44 percent said they were regular users in the past.

The researchers then compared each man's semen and hormone analysis to his reported marijuana use.

According to a team at the Harvard T.H. Chan School of Public Health, men who had smoked marijuana had higher sperm concentration and count than men who had never inhaled. The men gave sperm and blood samples, as well as answering questions about how often they smoked marijuana or used other drugs.

"These findings do not mean that using marijuana will increase sperm counts".

The study also found that among the men who had ever smoked pot, "those who smoked it more often had testosterone levels an average of eight nanograms per decilitre higher than those who used it less often".

Additionally, researchers of the current study said the doses of marijuana used by participants may have varied from the doses of participants in past studies, therefore skewing the results.

Meanwhile, those who had never light up a joint in their entire life recorded an average count of 45.4 million/mL and only five per cent of marijuana smokers had sperm counts below 15 million/mL. For men who smoke marijuana and are planning on having children, the advice keeps getting more confusing.

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

Other researchers have recently been warning about plummeting sperm counts among Western men.

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