Participants were also asked to complete a questionnaire about their marijuana use, including if they had ever smoked more than two joints - or the equivalent amount of marijuana in their life - and if they were current marijuana smokers.
"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", Chavarro said in a press release.
And this difference in physiology or other associated behaviours might then also be responsible for the difference in sperm counts, rather than the marijuana.
Feiby Nassan, lead author of the study and a postdoctoral research fellow at Harvard Chan School, told Newsweek: "Because the endocannabinoid receptors (the ones responsive to marijuana) are found in many places in the body especially the reproductive system, we need to understand their role on our health, especially with increasing their legalization".More news: Trump's call to end HIV epidemic hindered by his administration's policies
Men who had ever smoked marijuana had significantly higher sperm concentrations and sperm counts, as well as higher testosterone levels, compared to men who had never smoked weed. This had been the case in past studies, although most of those were very small, used animal models, or focused on men with histories of drug abuse.
Past studies have claimed that using the drug could lower a man's sperm count. In addition, men in the study self-reported their marijuana use, and it's possible that some participants were not truthful about their marijuana use, due to the social stigma or illegal status of the drug in MA at the time the data was collected.
However, the effects of more moderate marijuana use on sperm counts among men is less clear. Some studies indicate that using cannabis can harm the creation of sperm, while others suggest men who use the substance have higher levels of testosterone: the hormone involved in making the reproductive cells. In addition, a study from past year found that marijuana's active ingredient, THC, can change the structure and development of a sperm's DNA.
Researchers analysed health surveys from men who sought fertility treatment at the Massachusetts General Hospital Fertility Center between 2000 and 2017. What's more, all the of the men were enrolled at a fertility clinic, meaning they were seeking medical help with their partners to try to get pregnant. Only five percent of cannabis users had sperm counts below 15 million/mL, the World Health Organization's (WHO) threshold for "normal" levels, compared with 12 percent of men who had never smoked cannabis. The researchers also collected blood samples from 317 participants for the goal of analyzing reproductive hormones. Researchers warned that heavy cannabis use could bring sperm levels back down to normal. It's possible that low levels of marijuana could boost sperm quality, they say, while higher levels and repeated use could have a negative effect. 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.More news: Galaxy S10e Canary Yellow renders bring a ray of sunshine
Interestingly, each additional year that had passed since a man last used marijuana was tied to a slight increase in sperm count.
"Our results need to be interpreted with caution, and they highlight the need to further study the health effects of marijuana 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.More news: 2018 was the fourth-hottest year on record