Cannabis & Male Fertility: What The Science Says

The effects of medical cannabis on male fertility are complex and there’s a lot we don’t know yet. Part of the problem lies in the lack of human research – most studies on cannabis and male fertility are performed in vitro (not in a live test subject) or in animals.

This is understandable due to the obvious ethical concerns, but the human research that does exist suggests that you should avoid cannabis if you’re trying to conceive or worried about your reproductive health.

Such research has shown that cannabis may have some negative effects on human sperm production, quality and morphology. But limited studies have also shown potential beneficial effects on male reproductive systems and testosterone levels, so the evidence one way or the other is currently inconclusive.

The majority of evidence, however, tends to indicate that cannabis should generally be avoided if you’re looking to maintain optimal sperm health and reproductive function. ‍

How Is The Endocannabinoid System Involved In Male Fertility? ‍

The endocannabinoid system helps manage a variety of your bodily functions. The cannabinoids found in cannabis, mainly tetrahydrocannabinol (THC) and cannabidiol (CBD) influence the endocannabinoid system in several ways.

THC acts on cannabinoid receptors throughout the body, including those found in your brain’s pituitary gland and hypothalamus, both of which play crucial roles in the male reproductive process. Cannabinoid receptors have also been found in human sperm cells and testicular tissue.

Because of this, we know that the endocannabinoid system is deeply involved in our reproductive function and health. This means that cannabis may affect different aspects of the reproductive system, including sperm cells and hormones such as testosterone. ‍

How Does Cannabis Affect Sperm Production And Quality?

The available evidence mostly suggests that cannabis has a negative effect on human sperm production and quality, but the research is still in its early stages. However, there are some conflicting studies on cannabis and fertility that report some positive effects on sperm, especially when cannabis is consumed in low doses.

A systematic review published in 2019 looked at the published research and generally found that cannabis negatively affects semen quality, in particular by reducing sperm count, concentration and functionality.

There is limited human research available, several of the studies reviewed in the article were conducted on animals or done in vitro. The review emphasises the need for more high-quality studies on how cannabinoids might affect sperm and fertility in human models.

One of the few human studies with a large sample size on cannabis and male fertility was conducted in 2015 on 1,215 Danish men. The authors found associations between the 45% of participants who used cannabis and reduced sperm quality in regular users.  

Another study found that cannabis use may have actually increased sperm count and concentration among 662 human subjects. However, there were also associations between higher sperm count and subjects who were past cannabis users instead of current. Those who had abstained from cannabis for longer also had higher sperm counts. Due to these inconsistencies, the study’s authors state that the potential connection between higher sperm counts and cannabis may be due to other factors.

A more recent study found that after 11 weeks of abstinence from cannabis, many of the negative changes in sperm had reverted, indicating a period of abstinence from cannabis may be a good idea if you’re worried about your reproductive health. However, the number of participants was small and the researchers emphasise that larger studies are needed to confirm this.

How Does Cannabis Affect Sperm Motility and Morphology?

Sperm morphology refers to the size, shape and structure of sperm cells. Abnormal sperm morphology can lower the chance of a sperm successfully fertilising an egg, meaning it’s an essential component of male fertility. Sperm motility determines how effectively sperm can move, with low motility also potentially lowering the chance of conception.

A 2021 study of 409 male patients with fertility issues found that current and past cannabis users were significantly more likely to have abnormal sperm morphology compared to patients who had never used cannabis.

That cannabis affected past users’ sperm as well as present users means the effects on sperm morphology may be long-lasting, but this is mostly speculative. The amounts used and methods of cannabis consumption were also not always clear in the study, as the researchers relied on self-reported cannabis use.

The study’s authors concluded that cannabis may have a negative effect on sperm morphology and volume. However, they also found that cannabis may be beneficial for those who have sperm with unusual motility.

A recent study on 229 men with pre-existing fertility issues found that heavy cannabis use had negative effects on sperm morphology, but regular, limited use did not have the same negative effect. The researchers concluded that men with fertility issues could be more vulnerable to the negative effects cannabis may have on sperm compared to those with healthy reproductive systems. ‍

How Does Cannabis Affect Testosterone?

As it stands, there isn’t enough evidence to clearly demonstrate how and to what extent cannabis may affect testosterone levels. The available research does suggest that the amount of cannabis you use may determine how it affects your testosterone.

A 2018 study found that among the healthy male participants, those who had consumed cannabis within the last month had higher testosterone levels than those who hadn’t consumed it in a while.

The study also found that those who only consumed cannabis 1 to 3 times a month had higher testosterone levels compared to those who used cannabis daily. This suggests that recency of cannabis consumption, rather than duration or  frequency of cannabis use,  has the strongest impact on testosterone levels in males of reproductive age. ‍

Cannabis And Male Fertility: Making An Informed Choice

The current research around cannabis and male fertility suggests it’s best to play it safe and abstain from cannabis if you’re planning on having a child or worried about your reproductive function. The limited human research suggests that cannabinoids may have a negative impact on sperm production, quality and morphology as well as potential impacts on hormones such as testosterone.

The Therapeutic Goods Administration of Australia advises against medical cannabis products if you are trying to conceive. Speak with your doctor about alternative treatments to medical cannabis if you’re concerned about your reproductive health or if you're trying to conceive.