Dr. Matthew Hill

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614 appearances 1 recordings 1 series first heard Jul 2024 last heard Jul 2024

Dr. Matthew Hill’s voice in public audio — every appearance, attributed to the second.

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Huberman Lab · How Cannabis Impacts Health & the Potential Risks | Dr. Matthew Hill · 8 Jul 2024 podcast

I mean, we don't see, again, it's not like super clean relationships like we're seeing that were there when they established, you know, cigarette smoking and lung cancer kind of thing. I think that effect was so profound and the population of smokers used to be so high.

I would probably guess, and this is a guess, that anything, again, combustion smoke-wise, I mean, maybe not vaping plant matter, but at least the combustion from smoking probably exacerbates this just because any kind of combustion product is going to have some vascular effects to some degree on the system. So I imagine we'll make it worse.

But THC itself has a very complex effect on cardiovascular function because it tends to cause – typically vasodilation. So you get widening of the blood vessels, which is why it relates to a lot of people will experience postural hypotension. So sometimes when, what that is is if you stand up and your blood pressure doesn't catch up with you, so you get really lightheaded and people will collapse.

And so this is not uncommon to happen to people when, and with edibles as well. So it's not just from smoking. Um, But when they've consumed cannabis in some capacity, there are some people that seem to be very sensitive to the vasodilating effects. And so when they stand up, their blood pressure can't match the shifting gravity that happens.

It's a bit of a tricky thing because obviously if there is some underlying heart or a cardiac sensitivity or issue, the tachycardia itself can be a problem.

I mean, so like, you know, if someone has like an underlying heart condition where at rest it may not present itself, but the shifts into that kind of beating faster to compensate for the fact that you've got a drop in blood pressure can put strain on the heart in a way that could unmask a vulnerability or an event.

And again, this is me theorizing what I think it could be based on what we understand to some degree about how it affects cardiovascular function. There are occasionally people who have reported having like elevated blood pressure. I mean, some of that also could be from like an anxiety state or whatnot coming around.

But the typical response, and this is usually driven by cannabinoid receptors that are in the vascular beds themselves, that it causes a vasodilatory response. And so that is usually the first step. The second is the uptick in the heart rate. So you get these kind of effects over time. There's some work looking at like vascular stiffness that can evolve over time.

And cannabis users, there's some evidence to suggest that you might get more of that emerging. And so again, that could relate to a vulnerability to have strokes or other kind of cardiovascular events in that sense. So I think the issue in terms of like why it is more difficult for us to say anything definitively at this point is just obviously the timeline of this.

I mean, you know, cigarette smoking was an easier thing to establish in that context because, you know, once antibiotics and medicine advanced in like the 40s and the 30s and stuff and people started living longer, you started seeing a lot of these effects of cigarette smoking emerge.

Oh, I know. It's wild.

I mean my grandparents grew up in Belfast. They had smoked for years and they had even said like when they were younger, doctors would say, oh, have a cigarette after a meal. It promotes digestion. So it's kind of wild to hear that stuff when you think of how cigarettes are viewed nowadays. But –

It is, I don't think we've kind of been able to track this long enough to be able to say with certainty what we're seeing. But I think there's, like if people ask me about risks and harms of cannabis, the first thing I always say is, you know, schizophrenia and bipolar. Those are the main concern areas, I think, where you want to avoid cannabis.

And I would also say if anyone has cardiovascular issues, they should avoid cannabis just because that's more of like I would say a being safe because I don't know how to actually explicitly say what I would say the harms associated with it are. But I think there is something there. I've seen enough evidence that's like starting to coalesce into a story that's like there's something here. Mm-hmm.

So that's where I would say that I think there's risk. There's also things like this bizarre cyclic vomiting syndrome, which is this really strange thing that has become really apparent.

We've seen this in Canada a bit more now with legalization, again, because people are going into ERs more, where it's this somewhat strange phenomenon where it's usually people who are pretty excess cannabis users. They just start like puking and they can't stop it. And it's like this intractable vomiting that they get into.

And then bizarrely, like one of the things that seems to cure it is a hot shower, which is, I can't even begin to understand this.

I mean, I really struggled to understand because certainly I don't think it was doctors that figured this out. This was people, I think, who were experiencing this. And then they started telling doctors this. And then I think... And I can only imagine, I'm like, maybe they're going in the shower because they're like vomiting on themselves. Probably.

And then inadvertently realize that being in a hot shower somehow seemed to calm this down. I have seen a study where they actually applied capsaicin cream and that also seemed to provide benefit.

It's something with thermoregulation because the other thing that seems to have shown some benefit is propanolol. which again would suggest some kind of sympathetic. Which is a beta blocker. It's a beta blocker. So yeah, it's your effect. So there's something with autonomic. It must be messing up some kind of autonomic balance or something with thermoregulation.

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