As cannabis legalization spreads, more research investigates the potential impacts—both good and bad—of cannabis on health. One area receiving recent attention is male reproductive health, especially how weed influences sperm, hormones, and fertility.
With Canada’s 2018 legalization of recreational weed, scientists gained a unique opportunity to analyze effects before and after more access.
New data from a 20-year study of nearly 12,000 Canadian infertility patients sheds light on the implications for would-be fathers who smoke cannabis.
Shifting Social Substance Trends
Over two decades spanning 2001 to 2021, researchers documented significant shifts in substance use patterns among men seeking fertility evaluations.
As societal attitudes changed, recreational cannabis consumption steadily rose around 8% annually even prior to legalization.
Tobacco smoking and alcohol intake showed opposite trends, declining yearly as cannabis use increased.
“We observed more infertile men reporting cannabis use over time while fewer said they smoked cigarettes or drank alcohol,”
explains Dr. Malcolm Smith, lead study author and urologist focused on male reproductive health.
Comparing eras before and after Canada’s federal recreational cannabis legalization reveals even more striking trends. Among infertility patients, reported weed use jumped from 13% to 22%—a boost of over 70%—comparing pre- and post-legalization periods.
Conversely, tobacco smoking decreased from 18% to 15% between the era’s while alcohol use dropped from 55% down to 51% following recreational cannabis legalization.
“Canadian men clearly switched substances, substituting newly legal and accessible cannabis for tobacco or alcohol,” says Smith. “This reflects larger social shifts in recreational drug perceptions and choices.”
Impacts on Semen and Sperm
But what do these population-level recreational substance switches mean for individual health, especially fertility factors? Changes in sperm quantity and quality provide one window.
On average, the study found semen concentration (sperm count) declined between pre- and post-legalization eras. However, further comparisons between current cannabis consumers and non-users uncovered subtler dynamics.
“Despite lower sperm numbers overall, cannabis smokers actually displayed slightly stronger sperm mobility….So while weed associates with reduced semen volume or sperm output, it may boost performance in terms of movement or motility.”
explains lead author Smith.
I can present anecdotal evidence to this, in that I smoked for around 20 years solidly before having a child, without any issues.
Smith hypothesizes cannabis compounds could exert contradictory effects on cells involved in sperm production versus function.
Lower testosterone levels in weed smokers didn’t fully explain the semen patterns, highlighting the need to clarify biological mechanisms.
“The relationships between cannabis intake, reproductive hormones, and fertility biomarkers seem more complex than previously assumed,” says Smith.
“This should motivate more mechanistic research.”
Reconciling Conflicting Effects on Male Fertility
So does smoking cannabis ultimately benefit or harm male fertility factors? According to Smith, the results remain fuzzy.
“I hesitate to classify weed’s influence as wholly positive or negative. We found lower sperm counts yet enhanced motility in smokers, which seems paradoxical.”
He notes both sperm number and performance contribute to conception capacity, so impairments in either could reduce natural fertility.
For couples already facing challenges trying to conceive, even subtle shifts could impact outcomes.
However, moderate cannabis use didn’t appear to overwhelmingly worsen standard semen benchmarks.
Smith believes it wise for interested fathers or would-be dads to moderate rather than eliminate cannabis intake due to lingering uncertainty. He also calls for expanded study of epigenetic consequences in offspring depending on paternal weed use patterns.
Overall, Smith avoids blanket recommendations regarding cannabis and male fertility at this stage.
“We still have much to understand about marijuana’s hazards and hidden benefits surrounding male virility. But these initial concerning correlations warrant continued research as legal access expands globally.”
