Friday Weird Science: Cannabis, now coming for your sperm

Jun 01 2012 Published by under Friday Weird Science

Today's post is at the behest of Drugmonkey and Dirk, who turned me on to this paper. So for the hour I just spent reading about sperm preparations...thanks guys. Thanks a LOT.

But it turns out, I actually have quite a little pile of these cannabis and sperm papers, so maybe I'll do a little series! Get ready for your little swimmers to get hiiiiiiigh.

Morgan et al. "D9-Tetrahydrocannabinol (D9-THC) attenuates mouse sperm motility and male fecundity" British Journal of Pharmacology, 2012.

We often think about how cannabis, and its most famous ingredient, D9-THC (delta9-tetrahydrocannabinol) might impact our brains and behavior. But it's time for us to pause, and think about what's really important: our junk.

Yes, behavior and short term memory are one thing, but your SPERM! The very future of the species may hang in the balance of our pot-imbued balls.

But seriously, it is actually important to determine how D9-THC might be affecting fertility. Cannabis is very widely used, which makes it important to know all the possible effects. And if it can affect your sperm...well sperm, under the right conditions, meet eggs and turn into zygotes, which, with proper conditioning, turn into more people. While the long term effects of cannabinoids on subsequent offspring haven't been determined, figuring out how cannabis affects sperm itself is a good place to start.

And there's very good reason to look at sperm. D9-THC acts on the cannabinoid-1 receptor (CB1), and the cannabinoid-2 receptor (CB2). CB1 is present in mouse sperm, and human sperm has both CB1 and CB2. It's clear that sperm are meant to be sensitive to cannabinoids that are naturally present in the body (we call them the endocannabinoids).

But just what does D9-THC do to sperm? The authors of this study decided to look at sperm motility and energy (in the form of ATP). The took a bunch of mouse sperm, put it in a dish, and applied some D9-THC in a low concentration.

You can see above the measures of sperm motility. You can also see that D9-THC decreased the motility and the beating frequency of the sperm tail, which ended up producing decreased sperm velocity. Slooooooooooow sperm.

And that's all well and good. Don't put pot on your sperm in a dish. But what does that say about in vivo? To find this out, the authors gave a single injection of D9-THC (50 mg/kg, no word on how relevant this is to human dosing, though) to male mice, and let them get it on with some ladies. After mating, they kept track of the females, and looked at litter size (the number of pups), to see if the D9-THC had impacted fertility.

And so it did.

You can see on the left the normal mice and their litter sizes with vehicle or following D9-THC. D9-THC reduced the litter size by 20%, a pretty substantial reduction (say a normal little is 10 pups, well now it's 8). But you can also see that this effect depends on the presence of the CB1 receptors, CB1 knockout mice had no effects on litter size.

So it looks like, while the WiFi may not be coming for your sperm, with weed you may not be so lucky! But it still remains to be seen what will happen in humans, and if it affects human fertility like it does it mice.

...and luckily for you all, I've got a paper on that! Come back next week!

Morgan, D., Muller, C., Murataeva, N., Davis, B., & Mackie, K. (2012). Δ9-Tetrahydrocannabinol (Δ9-THC) attenuates mouse sperm motility and male fecundity British Journal of Pharmacology, 165 (8), 2575-2583 DOI: 10.1111/j.1476-5381.2011.01506.x

29 responses so far

  • Isabel says:

    Thanks for the scare story. Because we know how these things work, and what the headlines will say.

    Just what we need, at this crucial stage in the struggle against the American Inquisition, and with 50,000 dead in Mexico at last count.

    Up next - human race may soon go extinct due to the evil weed!

  • Isabel says:

    And really, Drugmonkey, addiction researcher, and Dirk, of the Addiction Box Blog???

    What does this study have to do with addiction? Why are they spreading the word, like this study which may have no relevance to humans, or bizarre, extremely rare case diseases? It certainly seems to support my view that they are just trying to tarnish the weed, and maybe keep the cash flowing?

    • scicurious says:

      Actually, they turned me on to it as something funny, not as something related to addiction. I did not mention addiction anywhere in the post.

  • Isabel says:

    case *studies*

  • Veryold says:

    Why such old research as something new. This was known at least 15-20 years ago. Something going on political. The effect is temporary by the way. After 3-12 months your sperm is running as it used to

  • RogerTheGeek says:

    Maybe the male mice were too interested in bagging some Cheetos to make a move on their partners. At 50 mg/kg for a human male, that would be a THC dose that would probably bring visions of ham sandwiches dancing on unicorns.

    A more serious question is why is there a reduction in litter size with THC. What's the mechanism that makes the sperm lower in velocity? Are there any open access links to research on such things? Googling doesn't get much other than people wanting to get pregnant.

  • DrugMonkey says:

    RTG: drug doses have to be scaled beyond mere mg/kg body weight. Doses that produce equivalent plasma levels, receptor occupancy and in vivo effects are generally higher in rat than in human.

  • Pascale says:

    Perhaps this is why the dinosaurs became extinct: they discovered weed and quit reproducing!

  • michael fons says:

    What about bob marley? He was a major pot head and had like 10 kids. Didn't seem to be hurting his sperm too much

  • leigh says:

    well, 50 mg/kg is a pretty substantial dose even in the rodent literature. i'd think that a chronic dosing study would be more relevant, as well, for a number of reasons.

    however, that is an interesting result. there are a number of cannabinoid-mediated events in implantation, so i'm curious what the effect would be in females.

  • Georgia says:

    Actually I am very Pro-cannabis and I liked your story and the honesty - It might be different in humans. Since they are Mice and we humans I bet it is.
    Anyhow - is it really a bad thing? Some natural birth control in this world?
    Starving, over populated world? Everything for a reason my friend.

  • Isabel says:

    "and the honesty"

    hahaha yes, people who post cannabis scare stories are "just being honest". And so hilarious!

  • john sparre says:

    in australia, the potheads, no not harry pothead the british royal, call the alcohol fans pissheads, piss being a colloqialism for alcoholic drinks. anyway, what is the effect on sperm of excessive intake of piss? none, because pissheads can´t get it up!

  • Sue Kenworthy @AndrologistUK says:

    The bottom line, which we already knew, is that cannabis makes sperm capacitate too soon, therefore they're already spent by the time they reach the egg, if they don't run out of steam first. Under the microscope, this fast tail beating and less effective forward progression, often with regular directional change, is described as hyperactivity and resembles a hammer drill action.

    In response to Michael, men with higher sperm counts have a better chance of having adequate functional sperm available. Bob Marley, bless his cotton socks, probably had a great sperm count - in my experience, the majority of cannabis-smoking men with no other male factors to infertility have good sperm counts with fast-moving sperm. The problem is going to be more apparent in men who have lower counts to start with. If cannabis affects say 50% (arbitrary figure) of sperm, 50% of not a lot to start with might just tip the critical mass required to a less fertile state.

    • scicurious says:

      Actually, it appears that cannabis doesn't make sperm have FASTER tail motion, it's in fact much slower than normal (see the first graph).

      • drugmonkey says:

        Maybe they are adjusting their speed to compensate for decreased navigational competence. Right Isabel?

      • Sue Kenworthy @AndrologistUK says:

        Motility in itself isn't a good description because standard practice for an andrologist (World Health Organisation guidance) is to grade moility into categories. For example rapidly progressive sperm travel linearly at >25um a second, sluggishly progressive sperm travel linearly but more slowly, non-progressive sperm are still motile but don't travel progressively. So saying motility decreases is not descriptive, but what we see with capacitation is that although the tail frantically beats, the linear velocity decreases. In addition, there is more directional change that may classify the sperm as non-progressive. This study may have been using rapidly progressive sperm only as its measure - can you tell from the methodology?

  • [...] scientopia Read [...]

  • Ace says:

    My pediatrician made me aware of similar studies over 10 years ago. However he also notified me that condoms and birth-control pills are significantly more effective, so that I would not depend solely on cannabis to prevent pregnancy, "I guarantee that (using cannabis as birth control) will not work," he said. And a lot of my friends have proven just that.

  • ariko says:

    not all readers have "little swimmers".

  • anon says:

    If D9-THC has such a detrimental effect on sperm motility, is it possible that giving men (or male mice) a CB1 antagonist would ENHANCE sperm motility? Are specific CB1 antagonists available?

  • [...] weeks ago I covered a study on cannabis coming for mouse sperm. But that's mice, not humans, and most of it was in a dish. So what does it mean for PEOPLE? After [...]

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