There is a popular narrative circulating around the anti-cannabis lobby – that increasing legal access to marijuana, medical or otherwise, will lead to a male fertility crisis with a sharp decline in testosterone and supercooled and rather directionless sperm.

However, if we turn to the available human data, any media hysteria about marijuana seems largely unfounded. Instead, evidence suggests that regular marijuana use may affect testosterone levels. Some studies suggest that regular marijuana use lowers testosterone levels, while other studies, on the contrary, correlate marijuana use with increased testosterone levels. The significance of the relationship between marijuana and testosterone levels is not yet fully understood.

CBD oil and testosterone

Before we get into most of what we know about cannabis and testosterone, it's important to be clear that we'll be talking primarily about THC, as very little research has been done on the subject. CBD oil and testosterone at this time.

Although a 2020 review of preclinical studies from the PubMed database suggests that “it can be concluded that CBD has a negative effect on the male reproductive system,” the authors were very clear that more research is needed to see if these less than favorable findings apply to humans and at what doses.

What is testosterone?

Testosterone, sometimes simply referred to as "T," is a male reproductive hormone produced primarily in the testicles. Although it's most often considered a male hormone, it's also produced in small amounts in women. It's responsible for many important functions, including sex drive, fertility, fat storage and burning, muscle mass, red blood cell production, and even mood regulation.

Most of us are familiar with the biological changes that occur in boys at the onset of puberty, and it probably won't surprise you to hear that the dramatic increase in testosterone production is responsible for deepening the voice, body hair, increased muscle mass, penis and testicle growth, and sperm production.1

In fact, during adolescence and the early twenties, testosterone levels peak, followed by a slow decline accelerated by factors such as alcohol consumption, exposure to toxins, obesity, heavy metals, and pesticides. Symptoms of low testosterone in men include low libido, erectile dysfunction, fatigue, depressed mood, loss of muscle strength, and brain fog.

Illegal drug use is often added to the list of contributing factors, but interestingly, commonly prescribed pain medications such as prescription opioids and even ibuprofen can also prematurely reduce testosterone levels in young men.2

While we generally think of testosterone as a male hormone, it also occurs in women, and vice versa. Estrogen, a form of the female hormone estrogen, can also play an important role in men's sexual health. Although present, it occurs in different amounts in men and women, and indeed, it is these gender differences in our hormones that experts believe may contribute to the differences in how men and women feel about marijuana.

Marijuana, Testosterone, and the Endocannabinoid System

The average marijuana consumer probably doesn't spend much time thinking about the biology behind the high they experience.

In fact, it wasn't until the 1990s, when scientists discovered the endocannabinoid system (ECS), a vast network of specialized receptors in our brains and bodies activated by marijuana-like chemicals, that even the scientific community began to understand the intoxicating effects of marijuana. They realized that THC fits these receptors like a key that opens a lock, which in turn triggers a cascade of effects throughout the body.

The endocannabinoid system itself is understood as a homeostatic regulator, constantly working to maintain balance in all physiological systems. Endocannabinoid receptors are found not only in the male reproductive system, such as the testicle, prostate, vas deferens, and sperm, but other components of the ECS, such as the endocannabinoid anandamide and the enzyme responsible for its degradation, fatty acid amide hydrolase (FAAH), have also been found in testicular tissue.

The fact that the Leydig cells, from which testosterone is released, also contain CB1 endocannabinoid receptors led researchers to conclude that the ECS plays an important role in maintaining healthy levels of testosterone production.

Interestingly, a 2001 study on mice found that anandamide, which acts similar to THC By binding to CB receptors, it suppresses testosterone levels, which perhaps fuels the theory that THC must do the same. 4

THC and testosterone – the evidence

While many preclinical studies in animals have suggested that THC administration lowers testosterone levels, human studies have been much less conclusive and have failed to prove that marijuana lowers testosterone.

In a 2018 study designed to assess the impact of marijuana consumption on American men, 1,577 men were asked about their frequency of marijuana use and compared it to their serum testosterone levels.

No difference in testosterone levels was detected between men who had used marijuana at some point in their lives and those who had never tried it. However, serum testosterone levels were higher in men who had recently used marijuana, indicating that any changes were related to the recency of marijuana use rather than the duration or frequency. 5

In Denmark, however, a study of 1,215 young men found rather conflicting results regarding the effects of marijuana on male reproductive health. On the one hand, sperm concentration and sperm count were almost 30% lower in those using marijuana once a week, while, rather counterintuitively, testosterone levels were higher and in the same range as cigarette smokers (smoking tobacco has been found to increase testosterone levels). Further research is needed to examine the effect of smoking marijuana with tobacco on testosterone levels compared to other methods of consumption. 6

Can exposure to cannabis during pregnancy affect testosterone levels in the fetus?

One area that will undoubtedly spark debate is whether marijuana is safe during pregnancy. Although the jury is still out and the evidence is scarce, one study investigated whether administering THC to expectant mother mice on day 12 of pregnancy would affect testosterone levels in their male offspring. At least in that study, testosterone and luteinizing hormone levels were significantly reduced, while CBD administered on the same day resulted in suboptimal testicular weight.

For ethical reasons, it is unlikely this study will be replicated in humans, but at least it raises awareness that what a mother consumes during pregnancy, whether it be cannabis or coffee, can have a direct impact on her baby.

Can marijuana use affect sex drive?

The fact that recent marijuana use appears to increase testosterone levels seems to disprove the theory that marijuana suppresses male libido.

Once again, numerous studies in animals, from rodents to primates, suggest that THC is at least somewhat of a passion killer. However, when it comes to humans, once again, nothing has been conclusively proven.

Several studies have linked marijuana use to premature ejaculation and erectile dysfunction (ED). When 8,650 Australian men were surveyed about marijuana use and its sexual effects, daily use was correlated with poorer sexual and erectile function. Women did not experience the same effects of marijuana use and may actually be more likely to achieve orgasm if they use marijuana. 7

Correlation does not imply causation

When it comes to marijuana and testosterone, it seems like this may be another case of correlation not implying causation. Yes, overall testosterone levels may be declining in the West, and male infertility may indeed be increasing, but increased marijuana consumption is likely not to blame, and certainly not the primary cause. Instead, countless factors, such as opioid abuse, pesticide use on crops, and rising obesity levels, may play a role.