Cannabis use is on the rise. So it is no surprise that a number of new health benefits and risks are becoming known from this controversial plant. But how does marijuana affect male fertility?

The American Society for Reproductive Medicine notes that there have been just a few clinical studies conducted on the affect of marijuana on male fertility. And the results? Well lets just say that they seem to be all over the place.

Most studies seem to suggest that that cannabis use is detrimental to male fertility. One 2015 Danish study revealed that Danish men who smoked marijuana more than once a week had lower sperm counts. From this study, marijuana appears to have negative effects on sperm count, sperm morphology, and sperm motility – all of which are, of course, very important for getting pregnant.

A later study found that marijuana’s active ingredient, THC, has the ability to change the structure and development of a sperm’s DNA. A particularly concerning study found that a specific gene associated with autism appears to undergo changes in the sperm of men who use marijuana. Whether those changes can be passed on to a child remains unknown, but for now, some researchers are warning that men in their childbearing years should consider how weed might impact their fertility and possibly their offspring.

But other studies have lead researchers to opposite conclusions. A recent Harvard University study found that men who have smoked marijuana at some stage in their life seemed to have higher concentrations of sperm than those who had never had a puff.

Another study revealed that Marijuana could potentially serve as a treatment option for male infertility. From their results it appeared that the same type of receptors in the human brain and body that respond to cannabis (what we call “CB2” receptors) are also responsible for regulating sperm, researchers publishing in The FASEB Journal discovered.

About 50 percent of infertility cases are due to male infertility. Drug treatment programs — including hormone replacement therapy — are currently options for treatment, but their effectiveness isn’t ever guaranteed. Researchers behind this study hope their findings will lead to the development of medicines that chemically mimic the behaviour and effects of cannabis.

There’s also a lot of debate over marijuana’s impact on male testosterone. When it’s time to start a family, testosterone is crucial as testosterone is a key hormone in sperm production. Studies have shown that marijuana increases testosterone and other sex hormones but then it causes a sudden testosterone drop, well below normal levels. Though much more clinical research is needed to understand just how marijuana impacts basic reproductive functions, the sudden spikes and dips in hormones seen among marijuana smokers may be partly to blame for low counts.

So where does that leave us? Confused? I sure am. It seems the jury is still out on whether or not we should be jumping on the cannabis band-wagon. I think I'll wait for some solid evidence before lighting up.


Payne KS, Mazur DJ, Hotaling JM, Pastuszak AW. Cannabis and Male Fertility: A Systematic Review. J Urol. 2019;202(4):674-681. doi:10.1097/JU.0000000000000248

Nassan FL, Arvizu M, Mínguez-Alarcón L, et al. Marijuana smoking and markers of testicular function among men from a fertility centre. Hum Reprod. 2019;34(4):715-723. doi:10.1093/humrep/dez002