Smoking small amounts of cannabis has been linked to a higher sperm count in men, new research has found.
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 in the study reported smoking an average of two joints per week.
The results, published in the journal Human Reproduction, shocked the research team because they were “not consistent with a deleterious role of marijuana smoking on testicular function as initially hypothesized.”
The Harvard researchers collected 1,143 health surveys and semen samples from more than 650 men between the years of 2000 and 2017. All the men were seeking treatment at the Massachusetts General Hospital Fertility Center. On average, the subjects were 36 years old, white and college educated.
The survey asked the men about past and present drug use, as well as other lifestyle choices. Fifty-five per cent reported having used cannabis at some point in the past, and 11 per cent said they currently used the drug.
The study also found that men who smoked cannabis in the past had slightly higher sperm counts than those who reported using the drug at present.
In an interview with Time, co-author and Harvard associate professor Dr. Jorge Chavarro, stressed that this does not mean using marijuana will increase your sperm count. While he’s not certain of the drug’s impact on male fertility, he believes it’s more likely that men with higher testosterone levels will be more inclined to use marijuana.
“It is well-documented that within normal ranges, high testosterone levels are associated with greater engagement in risk-seeking behaviours, including drug use,” he says.
Previous studies have linked heavy cannabis use to lower testosterone levels and a decline in both sperm production and quality. One 2014 study surveyed nearly 2,000 British men and found that men under 30 with less than four per cent normal sperm were twice as likely to have used marijuana in the past three months.
However, Chavarro noted that some of those past studies surveyed men who use multiple drugs at once, making it difficult to pinpoint the effects of marijuana alone.
“There seems to be a lot going on in terms of legalization, but not an equally fast pace in terms of knowing what the health effects of marijuana might be,” Chavarro added. “We’re essentially operating on a very-little-data-scenario.”