With cannabis now legal in much of the US, the focus is shifting from the ethics of using the drug to the health implications. New research suggests smoking cannabis doesn't lower sperm quality, challenging the results of some previous studies.
Semen samples from 921 men were analyzed as part of the study, which was led by researchers from the Boston University School of Public Health. The samples were checked for semen volume, total sperm count, sperm concentration, and sperm motility (how well the sperm can move and swim, which affects fertility).
Overall, the researchers found no significant difference in these measurements when comparing cannabis users with people who don't use cannabis. While there were variations, they didn't meet a statistically significant threshold.
"Chronic cannabis use among human males has been associated with lower testosterone concentrations and alterations in other hormones relevant to semen quality," write the researchers in their published paper.
"Studies have also shown associations of chronic cannabis use with poor semen quality, but results have been inconsistent across different hormonal and reproductive measures."
In this sample at least, there was no pattern to be found. It doesn't settle the issue one way or the other, but it is another useful piece of evidence for scientists looking into the potential health issues associated with cannabis.
Previous research has raised questions around cannabis use and how it might influence working memory and trigger psychotic experiences. Other research has suggested cannabis use could protect against cognitive decline. It definitely seems to leave lasting changes to our bodies, for better or worse.
When it comes to this particular study, 22.6 percent of participants said they were regular cannabis users, while 3.3 percent of them said they used cannabis every day – but this use apparently had no impact on sperm health.
"Further control for potential confounders, including body mass index, had little influence on the study results and results were similar among non-smokers of tobacco," write the researchers.
We know that the primary psychoactive ingredient in cannabis, delta-9-tetrahydrocannabinol (often referred to just as THC), interacts with cells in many different parts of the body – including the brain, of course, but also other tissues and organs.
Importantly for this particular field of research, we've also seen THC affecting the testes in animal studies. With that in mind, it's somewhat surprising to see no noticeable impact on sperm health in the sample of men tested here.
More research is going to be needed to establish whether cannabis use really does impact sperm quality – across larger groups of men, across longer timeframes, and across more countries. With more data, more recognizable patterns should appear.
"There is a paucity of information regarding the effects of cannabis use on semen quality," write the researchers.
"Epidemiologic studies of cannabis use and semen quality have been limited and results have been inconsistent."
The research has been published in Andrology.