Health
This common habit could be quietly hurting men’s fertility, experts warn
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As the Trump administration moves to loosen federal restrictions on drugs — including a new step to ease regulations on state-licensed medical marijuana — questions are growing about cannabis use and its broader health effects.
Among them is a lesser discussed concern: men’s fertility.
During National Infertility Awareness Week, experts are drawing attention to the potential negative impact of both recreational and medical cannabis on male reproductive health.
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Cannabis use has been associated with changes in reproductive health for both males and females, though human evidence remains mixed.
“This is especially disheartening when men and women are actively trying to conceive and start a family,” Dr. Alta DeRoo, chief medical officer of the Hazelden Betty Ford Foundation in Minnesota, told Fox News Digital.
As the Trump administration moves to loosen federal restrictions on drugs, questions are growing about cannabis use and its broader health effects. (AP Photo/Martin Meissner, File)
A 2025 Harvard-linked study involving women undergoing fertility treatment revealed twice as many miscarriages among those using cannabis compared to non-users.
It’s a common misconception, however, that fertility issues are always due to an issue with the woman. Male infertility is more common than many think, according to Stephanie Seminar, MD, chief of the Reproductive Endocrine Unit at Massachusetts General Hospital, a founding member of Mass General Brigham in Boston, Massachusetts.
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“Many individuals think infertility is a woman’s problem, [but] male infertility is common and under-evaluated,” Seminar told Fox News Digital.
Out of the 10% to 15% of couples worldwide who experience infertility, male factors cause or contribute to approximately 45% of those cases, data shows.
Cannabis use, particularly when heavy and chronic, can have negative effects on male fertility, a doctor cautioned. (iStock)
Having normal sexual drive and performance does not mean that a man has normal fertility, Seminar noted.
An evaluation of male infertility goes beyond semen analysis, examining factors like sexual dysfunction, toxin exposure, tobacco/cannabis use, childhood illnesses and past testosterone use, according to medical experts.
How cannabis may affect male fertility
Cannabis use, particularly when heavy and chronic, can have negative effects on male fertility, Seminar cautioned. Those can include changes in reproductive hormones and semen parameters, including decreased sperm counts or mobility.
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Cannabis can also impact sperm quality, the doctor said. “The sperm count or volume can be lower, and those sperm produced may be malformed and unable to swim effectively,” the doctor said.
Research supports this decline – a 2019 review published in The Journal of Urology found associations between cannabis use, especially the smoked form, and reduced semen quality.
“Many individuals think infertility is a woman’s problem, [but] male infertility is common and under-evaluated.”
Another study of 1,215 healthy young Danish men, published in the American Journal of Epidemiology, found that smoking cannabis more than once per week was associated with a 28% lower sperm concentration and 29% lower total sperm count.
Combining marijuana with other recreational drugs more than once a week reduced sperm concentration and count even higher – by 52% and 55%, respectively.
Disruption of reproductive hormones
The human body produces its own natural endocannabinoids to regulate vital functions like fertility, as described in a Nature Reviews Urology analysis.
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Cannabis mimics these molecules with its two main compounds: cannabidiol (CBD) and THC (tetrahydrocannabinol), which interact directly with the body’s endocannabinoid system.
Cannabis may interfere with the brain’s regulation of reproductive hormones, experts say. (iStock)
While THC can relieve pain or stimulate appetite, it also triggers the “high” that often leads to adverse side effects, like anxiety or paranoia, which have been widely documented in cannabinoid research.
When cannabis is consumed, external cannabinoids enter the body and bind to the same receptors as natural endocannabinoids, which may impair sperm quality and reproductive function, according to previous studies.
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Cannabis may interfere with the brain’s regulation of reproductive hormones, with some research suggesting it can alter levels of FSH (follicle-stimulating hormone) and LH (luteinizing hormone), which signal the testes to support sperm production.
This hormonal suppression could contribute to fertility challenges in some cases, though researchers noted that human evidence remains mixed and continues to be studied.
Potentially reversible
Men planning to conceive should stop using cannabis, experts recommend, as it can significantly impair sperm quality, with higher usage correlating to worse outcomes.
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Any negative effects may be reversible, as fertility can be improved when couples stop cannabis use, DeRoo noted.
Experts recommend discontinuing cannabis use at least three months prior to conceiving to allow the body to generate a full cycle of healthy sperm.
Men planning to conceive should stop using cannabis, experts recommend, as it can significantly impair sperm quality. (iStock)
The American Society for Reproductive Medicine also encourages couples trying to conceive to avoid recreational drugs to maximize their chances of a healthy birth.
“Stopping the use of cannabis improves other areas of health in a person’s life, and conception or pregnancy can be a strong motivator for abstinence,” DeRoo added.
Cannabis use in the US
In 2021, nearly one in five Americans (52.5 million people) used cannabis, making it the most common federally illegal drug in the country, per CDC data.
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Statistics show that about 30% of users may develop cannabis use disorder at some point, which adversely impacts their daily activities.
Recreational cannabis is legal in roughly half of U.S. states, while medical marijuana is legal in a large majority (well over 30 states), according to the CDC. A small number of states still prohibit most forms of cannabis use.
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A common over-the-counter medication combined with a home exercise program could help ease cognitive issues for cancer patients.
That’s according to a study from the University of Rochester, which tested the effects of physical activity and low-dose ibuprofen on patients receiving chemotherapy treatment.
“Chemo brain” (also called chemotherapy-related cognitive impairment, or CRCI) is a known side effect of cancer treatment that can affect memory, concentration and multitasking ability. Up to 80% of people who receive chemo experience some degree of cognitive impairment, previous studies have shown.
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Rochester’s phase 2 trial studied 86 adult cancer patients in New York undergoing chemotherapy who were experiencing cognitive problems. The average age was 53 and nearly 89% of participants were women, according to a university press release.
Participants who took only ibuprofen also showed greater cognitive improvements than the placebo group. (IStock)
Patients were randomly assigned to one of four groups. One group participated in home exercise designed specifically for cancer patients, a second group combined the exercises with ibuprofen (200 milligrams, or one pill, twice a day), the third group took ibuprofen alone and a fourth took a placebo alone.
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The exercise program consisted of low to moderate-intensity activity, including progressive walking and training with resistance bands.
“This is one of the first studies specifically designed to assess these interventions for cancer-related cognitive impairment during chemotherapy in patients with multiple diseases using both performance-based cognitive assessments and patient-reported outcomes,” said lead author Michelle C. Janelsins, Ph.D., MPH, of the University of Rochester and the Wilmot Cancer Institute, in the press release.
Up to 80% of people who receive chemo experience some degree of cognitive impairment.
After six weeks, exercise was linked to the clearest improvements in attention and cognitive function, according to input from family and friends. Those in the group who combined exercise and placebo showed better attention levels compared to those who took just a placebo.
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Participants who took only ibuprofen also showed greater cognitive improvements than the placebo group.
The findings suggest that ibuprofen may provide some improvement in cognitive function, although the benefits appeared to be smaller and less consistent than those seen with exercise.
“Chemo brain” (also called chemotherapy-related cognitive impairment, or CRCI) is a known side effect of cancer treatment that can affect memory, concentration and multitasking ability. (iStock)
This suggests that inflammation may contribute to cancer-related cognitive impairment, and that anti-inflammatory medications could be an effective therapeutic approach.
“We are encouraged by the findings of this trial that suggest possible benefits of both interventions for some cognitive domains,” Janelsins said. “Clearly, we saw a more pronounced effect with exercise, which is notable considering the multiple health benefits of exercise for cancer survivors.”
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No adverse side effects were reported during the trial.
The findings were published in Cancer, the peer-reviewed journal of the American Cancer Society.
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There were some limitations of the study, the researchers noted, including the small sample size and short duration. The effects were also not consistent across every measure of cognitive function.
As the majority of participants were women, the findings may not be generalized to broader populations.
“Clearly, we saw a more pronounced effect with exercise, which is notable considering the multiple health benefits of exercise for cancer survivors,” the researcher said. (iStock)
Researchers are planning larger phase 3 trials to confirm whether ibuprofen and exercise can effectively improve chemo-related cognitive impairment.
“Since we saw cognitive benefits in some domains and not others, we will also consider additional doses and longer durations in future research trials,” said Janelsins.
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Investigators emphasized that patients should speak with their oncology team before starting ibuprofen or exercise interventions during chemotherapy, as certain treatments or medical conditions could increase the risk of side effects and complications.
U.S. health officials are monitoring 16 additional people across the country for symptoms of hantavirus whom the Centers for Disease Control and Prevention has not previously mentioned, the agency said on Thursday.
The new people the C.D.C. reported were not on the cruise ship but were passengers on an April 25 flight to Johannesburg and exposed to someone known to have been infected, said Dr. David Fitter, who is leading the C.D.C.’s response to the outbreak.
The new total of those being monitored in the United States is 41, a significant increase over the 18 passengers from the Dutch cruise ship who were brought back to the United States on Monday. They are quarantining at special facilities in Omaha and Atlanta.
Seven other passengers from the cruise ship had disembarked on April 24 in St. Helena, an island in the Atlantic Ocean, returned to the United States on commercial flights and are being monitored by state health departments.
As of Thursday, there were no confirmed cases in the United States, Dr. Fitter said.
The infected passenger was a 69-year-old Dutch woman whose husband was the first person to die in the outbreak, on April 11. She was among those who disembarked from the ship on April 24. The next day, she flew from St. Helena to Johannesburg. She collapsed shortly after arrival and died on April 26. She was confirmed on May 4 to have had hantavirus.
C.D.C. officials would not give any other information about the 16 passengers, including where they had gone once they reached the United States.
It was not clear whether all Americans exposed to the virus are now back in the country, or whether there are additional people being monitored abroad.
“Our job is to ensure that we are monitoring and in contact with anybody that might have been on the flight this person had taken,” Dr. Fitter told reporters. The agency is “monitoring all Americans that potentially would have been exposed, whether in the U.S. or abroad, and we have been in contact with them,” he said.
In an interview on Sunday with CNN, Dr. Jay Bhattacharya, the C.D.C.’s acting director, said none of the seven passengers who returned to the United States earlier had symptoms at the time of their travel, so officials had not seen a need to alert the public or trace contacts.
For the moment, quarantine is essentially voluntary. Officials are encouraging those who were exposed to the virus to “stay at home and avoid being around people during their 42-day monitoring period,” Dr. Fitter said.
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Concerns about rising hantavirus cases has Americans reflecting on the coronavirus pandemic.
Although COVID-19 began with a foreign strain and spread rapidly around the world, experts say it’s not likely that hantavirus will behave the same way.
The rare Andes virus, which was linked to the MV Hondius cruise ship outbreak, is the only known hantavirus strain that has the capability to spread from person to person, usually through prolonged close contact.
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Fox News senior medical analyst Dr. Marc Siegel spoke with Fox News Digital about the similarities and differences between hantavirus and coronavirus, noting that there is “no comparison.”
“You could say the comparison ends at that they’re both single-stranded RNA viruses,” he said. “That’s a comparison, but [hantavirus] has been unchanged basically for decades.”
Dr. Marc Siegel says there’s “no comparison between these two viruses, other than that the single-stranded RNA viruses are both carried by animals.” (iStock)
Coronavirus was different because it began to mutate, which started to cause “all kinds of problems,” Siegel noted.
“We don’t know why it started to mutate, but this one doesn’t appear to have done that,” he said. “And every day that goes by seems to show that theory is correct – the genetics of it is the same.”
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“So, there’s no comparison between these two viruses, other than that the single-stranded RNA viruses are both carried by animals.”
Siegel added that COVID is an airborne virus, while hantavirus is mainly a secretion-borne virus, although it can be transmitted through dust and droppings in the air.
The rare Andes virus, which was linked to the MV Hondius cruise ship outbreak, is the only known hantavirus strain that has the capability to spread from person to person, usually through prolonged close contact. (Andres Gutierrez/Anadolu)
“It’s not airborne … in terms of respiratory droplets hanging in the air,” he said. “It’s very difficult to transmit.”
While coronavirus “moved in the direction of humans in a significant way,” hantavirus has not, except for “very rare” human-to-human transmission, according to the doctor.
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There have been hantavirus cases in the U.S. for decades, although they are “very rare,” Siegel noted.
Certain factors of this disease spread are changing, including warming temperatures that are causing rodents to migrate north toward Buenos Aires, according to the doctor.
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The current outbreak stemming from the cruise ship did not help the cause, Siegel went on — but this spread doesn’t suggest that the virus has changed. Rather, it shows how close quarters on a ship are “very conducive” to spread, he said.
Passengers disembark from the hantavirus-stricken cruise ship MV Hondius at the port of Granadilla in Tenerife, Canary Islands, Spain, on May 10, 2026. (AP Photo)
“Every day that goes by shows that … we’re not seeing a second generation of spread,” he reiterated.
The better comparison to make is between hantavirus and bird flu, which is a predominantly animal-based virus that “occasionally infects humans,” Siegel said.
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“There are billions of birds, and every year we talk about how it’s going to cause a pandemic, but it would have to mutate significantly,” he pointed out. “I feel that [hantavirus] would have to mutate significantly before it could go human to human in any significant way, because this is basically an animal virus … it’s very comfortable inside a rodent host.”
Siegel went on, “If you get this virus, you’re in trouble, but getting this virus is very difficult.”
A person visits a COVID testing site on a Manhattan street in New York City on Jan. 21, 2022. “Coronaviruses are airborne … this is not,” Dr. Siegel said. “And coronaviruses mutate a lot, and this does not.” (Spencer Platt/Getty Images)
Regarding fears that another global pandemic may be looming, Siegel said that just because one virus becomes widespread does not mean all viruses will.
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“Coronaviruses are airborne anyway. This is not. And coronaviruses mutate a lot, and this does not,” he said. “I’m much more concerned about flu than this. Flu can mutate all the time, and it’s already going human to human all over the place, and it’s airborne.”
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“Most infectious disease specialists are much more worried about flu than this, as deadly as this can be,” he added.
“We’re talking apples and oranges, and any comparison you make after that provokes fear.”
Fox News Digital’s Melissa Rudy contributed to this report.
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