Cannabis Use Decreases Sperm Count But May Enhance Sperm Motility

The effects of cannabis on male fertility are somewhat confusing. Image: ShutterDivision/Shutterstock.com

Getting stoned has some strangely paradoxical effects on a man’s sperm, with some aspects of semen quality appearing to suffer as a result of cannabis use while others may be enhanced. According to a new study in the journal Therapeutic Advances in Urology, guys who smoke weed can expect a lower sperm count and a greater likelihood of deformed sperm, although their depleted legion of gametes may benefit from greater motility.

The impact of cannabis on sperm quality has been debated by scientists for some time, and previous studies have thrown up some pretty contradictory findings. For instance, research involving 1,215 recreational drug users in Denmark found that regular cannabis consumption was associated with a 30 percent reduction in sperm count. In contrast, however, a study involving 662 men attending a fertility clinic in Massachusetts concluded that cannabis users tended to have a higher sperm count than those who had never tried the drug.

In an attempt to settle the dispute, the authors of this latest study quizzed 409 men at a fertility clinic in Washington state about their previous cannabis use. A total of 174 claimed to have tried the drug at some point in their lives, with 17 percent of the cohort identifying as current users.

Compared to men who had never smoked a joint in their lives, current users were twice as likely to exhibit abnormal sperm morphology. Interestingly, however, oddly-shaped sex cells were even more common among past users than current users, which the study authors suggest may indicate “a delayed negative effect of marijuana on sperm morphology.”

Sperm count was also down among both past and current users, with weed smokers being three times more likely to suffer from low semen volume than those who had never sampled a spliff.

Paradoxically, though, cannabis use was associated with greater sperm motility, and those who claimed to enjoy a puff were more likely to fall within the normal range for this parameter. “This suggests a partially pro-spermatogenic effect [of cannabis]… the mechanism of which is not apparent,” writes the study authors.

Having said that, the researchers go on to explain that the reduced semen volume among cannabis users often leads to a reduction in total sperm motility, which refers to the absolute number of mobile sperm in the entire ejaculate. Given that total sperm motility is considered to be the major contributing factor to male fertility, the study authors ultimately conclude that smoking weed probably isn’t a good idea when trying to start a family.

While such a deduction may sound like common sense, the researchers do concede that their findings should not be considered irrefutable, due to the fact that their study involved a relatively small number of men from a single fertility clinic, which may not be representative of the overall population. Furthermore, their analysis didn't factor in other key influencers of male fertility, such as diet, exercise, or use of other recreational drugs, all of which may have had an impact on the quality of sperm delivered by the study participants.


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