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Cannabis is the most commonly used drug in the United States, consumed in some form or another by an estimated 48.2 million people, or about 18% of Americans. While many people use marijuana recreationally, there are also medicinal uses that range from reducing pain to alleviating nausea and aiding weight loss. There’s some evidence that marijuana can reduce tremors associated with Parkinson’s disease, improve cognition in patients with dementia, and even ease stress and anxiety.
However, research suggests that marijuana products may have a negative impact on male fertility. Find out how cannabis affects male fertility, what studies say about CBD, and considerations if you’re trying to conceive.
Most studies show that regular cannabis use is negatively associated with fertility and semen parameters. However, it is still unclear how cannabis may cause these effects and if occasional use has the same impact as chronic use.
It’s important to remember that lifestyle’s impact on fertility is a tricky thing to study, because of the many confounding factors affecting sperm health — and much of the research on cannabis has been performed in animal studies, due to research restrictions for controlled substances.
A 2020 systematic review on cannabis and male fertility concludes that cannabis use has a statistically significant impact on semen parameters and sperm quality, including lower sperm count and concentration, reduced sperm motility, and increased abnormal morphology. The review cited one study of dogs that showed a stark connection between daily administration of cannabis and a complete halting of spermatogenesis (sperm production), resulting in infertility after one month.
A 2015 study of 1,215 Danish men found that men who reported using marijuana more than once per week had a 28% lower sperm concentration and a 29% lower sperm count than men who had never used marijuana.
A much-publicized 2019 study of 662 subfertile men found an association between a history of marijuana use and increased sperm concentration (how many sperm per mL of semen). This was interpreted by some outlets to indicate that smoking weed can improve fertility. However, that’s not what the researchers conclude — they note that this study contradicts the bulk of other evidence, and that the role of chance or confounding factors can’t be excluded.
A 2013 study found a correlation between marijuana use and decreased sperm viability, the percentage of live sperm within a semen sample. Sperm motility, sperm’s ability to swim efficiently, is another factor potentially affected by cannabis use. Multiple studies have found that cannabis may reduce the mitochondrial activity of sperm, resulting in “significantly impaired” motility.
In terms of morphology (the size, shape, and structure of sperm), an animal study on male mice shows a correlation between marijuana use and various sperm abnormalities, such as sperm described as “banana-shaped” and “amorphous” with “folded or hookless heads.” Similar findings on abnormal morphology are noted in this study of men in the United Kingdom, which shows that men under 30 who had used cannabis in the three months prior to collection of a semen sample were more likely to have abnormal sperm morphology (defined as less than 4% normal sperm morphology).
Despite these abnormalities in morphology, researchers have found that cannabis use does not negatively impact genetic material inside sperm — called sperm DNA fragmentation — nor does it appear to increase pre-implantation loss or fetal mortality.
Studies of cannabis use and hormone levels are conflicting and limited.
A 2012 review concludes that cannabinoids such as marijuana interfere with reproductive functions by affecting luteinizing hormone (LH) in males and follicle-stimulating hormone (FSH) in females, hormones that stimulate sperm and egg production. In addition, the review states that cannabis impairs sex hormones such as a testosterone, estrogen, and progesterone. A study of 20 chronic marijuana users also suggests that men who use marijuana have lower testosterone levels. This is an important factor for fertility as testosterone, along with LH and FSH, is one of the male fertility hormones helping to drive the spermatogenesis process.
However, a study of 16 chronic marijuana users got different results. While researchers did find an association between marijuana use and lower sperm count, they did not find any hormonal changes in males. And another study found that testosterone levels were actually higher among cannabis users (semen parameters were still negatively impacted).
Cannabis may also have an effect on sexual behavior because of its impact on hormones, though findings differ between the sexes. A 2010 animal study shows that while cannabis may lead females to be more sexually receptive, it may lead to less sexual motivation or even erectile dysfunction in males.
Cannabidiol, or CBD, is the second most prevalent active cannabinoid in cannabis, after THC. Unlike THC, CBD does not have psychotropic properties and it is often used to reduce anxiety, alleviate symptoms of neurological disorders, improve sleep, and ease pain in muscles and joints.
But when it comes to fertility impact, CBD may not differ much from marijuana. After all, though most of the studies mentioned above specifically look at the consumption of products that contain THC, in some cases, the researchers conclude that it’s the cannabinoids in general that may impact fertility, not specifically THC. (And even if THC is the culprit, it should be noted that an FDA review found that approximately half of sampled CBD products actually contained detectable levels of THC.)
Though some manufacturers make claims that CBD can cure infertility and improve sperm health, these claims are not supported by scientific evidence. In fact, here is what the research does say about CBD and male fertility:
In a 2019 review of animal studies, CBD usage is associated with a reduction in testis size, the number of cells in spermatogenesis, fertilization rates, and hormone levels. Researchers also note that chronic doses of CBD have been shown to impair sexual behavior in mice. And in a 2018 animal study, there was a correlation between chronic exposure to CBD and lower testosterone levels, impaired spermatogenesis, and increased abnormal morphology.
Though further research is required to understand the full extent of CBD’s impact, evidence indicates CBD has overall negative effects on the reproductive system of males.
Does cannabis dose, form, or frequency make a difference?
The studies looking at cannabis use and fertility are extremely varied in terms of the dosage and frequency of use they use as a comparison. Some of the studies include unrealistically high doses. For instance, the 2015 study of 1,215 Danish men examines individuals who smoke 8-20 joints per day. This high frequency likely makes the study results inapplicable for those who are occasional, light users.
There is also not much data differentiating between types of marijuana consumption (smoking vs. edibles or tincture, for example). For instance, this 2020 study looking at chronic users who inhale (vape) marijuana found that even though THC was detected in semen, semen parameters were well within normal ranges. Is it possible that smoking presents unique issues for sperm production? This remains unclear.
Though cannabis may have valuable recreational and therapeutic benefits, both THC and CBD have been repeatedly shown in research to negatively impact male fertility. While there are still questions about how chronic vs. occasional marijuana use affects sperm health, and if method of consumption makes a difference, it’s best to reduce one’s usage of marijuana and CBD products while trying to conceive, especially if you have abnormal semen parameters.
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