How Smoking Weed Affects Sperm

Marijuana use in America is booming—only a few states still have no public cannabis access program. As of 2023, 38 states allow cannabis for medical use, and 24 states have made recreational use legal.

Marijuana (or weed) is the most commonly used drug in America. According to the Centers for Disease Control and Prevention (CDC), around 18% of Americans used weed at least once in 2019.

With its increasing accessibility, research on marijuana's health benefits and risks has also increased. And when it comes to fertility, researchers have looked at weed's impacts on sperm and sperm health.

So, does smoking weed affect sperm? Read on to learn how weed affects sperm count, mobility, DNA, and fertility.

How Weed Affects Sperm Count and Mobility

"Tetrahydrocannabinol (THC), the active compound of marijuana, binds to receptors in many different glands and tissues that are involved in sperm production," says Matthias Hofer, MD, a urologist in San Antonio, Texas. "These receptors are found in the hypothalamus and pituitary gland, decreasing hormone production necessary for sperm production."

When it comes to research, most studies have concluded that marijuana is not good for sperm.

"There are many lab studies showing negative effects of marijuana on sperm. There are surprisingly few human trials, but they all demonstrate that cannabis use reduces sperm concentration, sperm motility (ability to swim), or both," says Doron Stember, MD, assistant professor of urology at the Icahn School at Mount Sinai.

The lack of human trials is primarily due to the federal drug scheduling, which classifies marijuana as a Schedule I drug despite its legalization in most states. Schedule I classification means that researchers must meet strict federal requirements, including registering with the United States Drug Enforcement Administration (DEA), undergoing background checks, tracking and discarding drugs, and more.

Even so, some studies do exist. For example, a 2015 study evaluated the association between marijuana use and reproductive hormones and semen quality. Among 1,215 Danish participants aged 18 to 28, researchers found the following associated with those who regularly smoked weed more than once a week:

• 28% lower sperm concentration
• 29% lower total sperm count
• 52% reduced sperm concentration when weed was combined with other recreational drug use
• 55% reduced total sperm count when combined with other recreational drugs

How Weed Affects Sperm DNA

Besides the impact on sperm count and mobility, some research has found that smoking weed may fundamentally change the sperm itself.

A study published in the journal Epigenetics found that marijuana actually mutates DNA in sperm. The study, published in 2018, was the first to report disruption in DNA of sperm in people who use cannabis. Researchers suspect that these changes are likely due to the THC component of cannabis.

Researchers say the risks of exposure are exacerbated by two significant trends affecting cannabis use:

• Fewer young people than ever before consider regularly smoking weed as harmful.
• The potency of weed has significantly increased over the decades (the ratio of THC to cannabidiol has increased from approximately 14:1 to approximately 80:1 between 1995 and 2014).

How Weed Affects Sexual Function

An older 2010 study found that cannabis use decreased men's ability to reach orgasm, reaching orgasm too quickly or too slowly. However, more recent research has found the opposite.

For example, a 2023 study of 811 participants of all genders and sexual orientations found that people of all genders perceived that weed increased sexual function and satisfaction, including increased orgasm intensity.

Additionally, there have also been some studies that negate marijuana's adverse effects on fertility.

How Weed Affects Fertility

While studies have found that marijuana misuse has a negative effect on sperm, there is limited research evaluating moderate consumption levels. A 2019 study set out to examine how smoking weed affects sperm in those who had previously smoked marijuana versus those who had never smoked weed.

Researchers surprisingly found that those who had used cannabis had significantly higher sperm concentration than those who reported never using cannabis. There were also no notable differences in sperm concentration between current and past users.

Another 2017 study of 1,577 men showed that cannabis use was associated with—but did not necessarily cause—higher testosterone levels. Researchers noted that how recently someone had used weed had more of an effect on testosterone levels than how long or how often participants had used weed.

While this can complicate getting a conclusive answer about marijuana and fertility, doctors believe more research must be done.

"While the scientific evidence that THC negatively impacts fertility at many levels is abundant, it should be noted that some of these studies are limited by low patient numbers and that a subset of studies found contradictory results," says Dr. Hofer. "Clinical trials, the highest quality study type producing the most reliable results, have not yet been performed and would provide further clarification."

So if you smoke weed and have difficulty conceiving, marijuana use may not be the sole cause of your fertility issues.

"Fertility can be affected by many factors, and THC is just one of them," says Dr. Hofer. "Although there is ample evidence that sperm count and quality is affected by THC if considering fertility overall (lower sperm count may still be sufficient for conception), it appears that there is no difference in the probability of couples getting pregnant among those using marijuana compared to those that did not, according to a recent study."

The study Dr. Hoffer references is a 2018 study that evaluated the link between marijuana use in males and females and the chances of getting pregnant in one menstrual cycle. It found little overall association between weed use and chances of pregnancy.

The Risks vs. Benefits of Smoking Weed

So, does smoking weed affect sperm? And should people stop using marijuana if they're trying to conceive?

While the research has gone both ways about weed's effect on sperm, health experts do not generally recommend using marijuana. In addition to potential fertility concerns, the CDC lists the following possible negative health effects of marijuana:

• Addiction
• Negative impact on brain health (specifically memory, learning, attention, decision-making, coordination, emotions, and reaction time)
• Impaired driving
• Impact on heart health (increased heartbeat and blood pressure after immediate use, and increased risk of stroke, heart disease, and vascular disease)
• Lung damage from smoked weed
• Increased risk of mental health problems
• The risk of children getting into edibles because they mistake them for candy
• Accidental overuse, especially with edibles
• Second-hand smoke exposure to those around you

That said, the CDC also notes known potential benefits, like easing the side effects of cancer and cancer therapies. While the evidence is limited about weed's ability to treat pain, many people use it to find relief from chronic pain.