Cannabis and Sperm: Does Pot Impede Male Fertility?


In the first two seconds of doing research for this topic, Bob Marley popped into my mind.

I immediately thought “this can’t be right, Marley has a bunch of kids, and he’s the poster-boy (poster-rastaman would probably be a bit more fitting) of weed”.

I was aware that he had a lot of children, but once I double checked online, it turns out that the number comes to a total of 11 kids.

I don’t know how you feel about that, but in my book that’s a staggering number. But our feelings on his lifestyle choices are of no importance anyhow.

Of course, as one of the most positive and peace-inspiring artists of the modern age, it can be said that he was rock-solid dad material, so having that many offspring doesn’t really seem like an issue at all.

All jokes aside, it’s quite plausible that Mr. Marley was an exceptionally fertile individual, so any difficulties that cannabis creates with sperm just didn’t affect him sufficiently.

But when we look at the available hard facts, it quickly becomes evident that weed is indeed connected with lowering the sperm count and can even influence some rather erratic behaviour in the remaining “swimmers”.

Luckily all the available research doesn’t suggest any kind of long term negative effects, but the temporary problems cannabis is responsible for seem quite indisputable.

The science of stoned sperm

When it comes to the science of cannabis versus sperm, the biggest obstacle lies in the general lack of knowledge on the subject, as the effects of cannabinoids on the spermatozoa are still widely unresearched, and because of this not yet fully understood.

In the meantime, while we’re waiting for the scientists to figure out the how exactly cannabis does what it does to sperm, there are several studies from which we can draw some direct conclusions.

I’m going to summarize for you all the most important ones currently available, with links that lead to each individual study, respectively.

Each of these studies was conducted in a different country, and they mostly focused on a specific aspect of the cannabis-sperm correlation.

2003, Buffalo University, USA

This research was performed on the semen of 22 frequent cannabis users, who reported using pot at least 14 times a week, over a period of approximately 5 years, and also on the samples of 59 fertile non-users who already had biological children.

The study concentrated on the swimming ability of sperm cells when influenced by cannabinoids, and the results showed that the spermatozoa from frequent canna-consumers timed their swim irregularly, which ultimately caused the cells to prematurely lose too much energy, and subsequently fail to reach the female egg cell. (1)

In a completely different study, scientists from the same university also figured out that the sperm cells contain cannabinoid receptors (2), which reveals that naturally occurring internal endocannabinoids like anandamide play an important function in our reproductive system, beside many other things, like the regulation of the immune system, activating (or inhibiting) inflammation, neurogenesis and much more.

The cannabinoid receptors located on the sperm cells also give us some insight into how pot causes sperm to act differently, even though the definite process of what exactly happens is still far from our comprehension.

2017, University of British Columbia, Canada

In this newer study from last year, Canadian researchers led by Dr. Victor Chow (who’s an associate professor at the University of British Columbia Medical School), found that frequent cannabis consumption leads to a fewer number of sperm cells (the so-called sperm count), and that the remaining cells of the individuals who frequently consume cannabis also tend to perform atypical motions, causing them to swim in circles rather than the usual straight-line path towards the ovum. (3)

It should be noted that even in perfect conditions (without any negative outside stimulants), a large percentage of spermatozoa will always exhibit erratic behaviour, and will be shaped unusually.

The researchers also added that the sperm count was decreased by approximately one third in most subjects tested.

They advise that if you’re experiencing difficulties while trying to conceive a child, you should lay off cannabis for around three months’ time; the male body creates new sperm cells roughly four times a year, and unlike spermatozoa, it produces other nutrients and enzymes that the semen contains on a regular basis.

2012, Denmark

During the period of four years (2008-2012), Danish scientists took samples from 1,215 men (18 to 28 years of age) and interviewed them about their cannabis habits in the previous three months.

The scientists also inquired about the use of harder narcotics including cocaine and amphetamines like MDMA and Ecstasy, also in the last 90 days prior to the testing.

Besides the semen examination, researchers also took blood samples and organized various physical tests for the testees.

If the subject reported that he consumed cannabis (or combined pot with heavier opiates), he was asked to scale the frequency of his use, ranging from once a week, to multiple occasions during one week.

The results were insightful, as 45% of the 1,215 men reported that they consumed weed within the last three months, and around 10% combined it with other substances during that period.

For the men who used cannabis regularly (multiple times a week), the sperm count was lessened by 29% (compared to the examinees who reported less frequent use, or total abstinence), and for those who used other opiates (and marijuana), the number was a whopping 55% decrease in the overall sperm count. (4)

The team in charge of the research also took into consideration that there is a large possibility that lifestyle choices, such as alcohol consumption, cigarette smoking, caffeine intake, less exercising and so forth, differed greatly between the examinees who were consuming cannabis regularly, and those who did not.

All these factors can naturally lessen the fertility (and the general well-being) of an otherwise healthy individual.

2014, United Kingdom, Journal of Human Reproduction

In this particular study scientists observed samples from 1,970 men obtained from various fertility clinics across the UK.

At first this study didn’t focus on the cannabis aspect, but rather how various habits which include alcohol, cigarettes, exercise, weight (and the body-mass index), history of medical issues, and even the type of underwear worn all influence the quality and quantity of sperm cells.

The researchers were interested to find that from all these habits and factors, only one was closely connected with unusual sperm morphology, or in layman’s terms how the sperm was shaped, and what size it was.

Out of 1,970 men, 1,652 provided “proper” sperm samples (which means that around 4% of their semen was the appropriate shape and size).

The remaining 318 samples were deemed as abnormal, and when researchers started to look for patterns in the habits of the tested men, cannabis became the prime suspect.

Because the questioning wasn’t precise enough at the beginning of the study, scientists could only determine that if a testee was using cannabis three months before ejaculating, there was a great chance of morphological abnormalities in their sperm. (5)

As I previously mentioned, the exact mechanism of how exactly cannabis causes these changes in sperm is still heavily uninvestigated and therefore practically unknown, but some animal testing seems to point to a possible conclusion, says Allan Pacey, who’s the senior lecturer of Andrology at the University of Sheffield, and one of the main researchers involved in this study.

“I do know there is some work in laboratory animals that suggests [cannabis]can affect the way the DNA in the sperm is packaged together, and that’s significant,” Pacey says.

“When sperm are made, the DNA they maintain has to be packaged in the head very tightly, and when that process doesn’t work properly, you get an abnormal sperm. So the cannabis is maybe interrupting that DNA folding.”

Now that we covered all the essential studies on this subject matter, I wanted to share with you some sperm-fundamentals so to say, just so you can have a clearer picture of what exactly is going on down there, and also because there’s a ton of fascinating stuff about these little guys.

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