What does this study of cannabis and cardiovascular disease mean?
April 13, 2024 4:52 PM Subscribe
A study published in late February by the Journal of the American Heart Association noted as its conclusion, "Cannabis use is associated with adverse cardiovascular outcomes, with heavier use (more days per month) associated with higher odds of adverse outcomes."
As far as I can tell, IANAD, frequency/day of cannabis use doesn't seem to have been taken into account. Intuitively, it would seem that taking a single bong hit vs. smoking multiple joints in a day would be substantially different, but it seems that the study only asked participants how often they used cannabis as in never/sometimes/daily. It also didn't appear to distinguish between methods of consumption, e.g., vape vs. smoke vs. edible.
The results are concerning, certainly, for cannabis users, especially among older users who are the biggest growth group in terms of cannabis use, I believe, and I wondered if any MeFites with greater knowledge of the topic could note the real-world significance and/or flaws in this study. Thanks.
As far as I can tell, IANAD, frequency/day of cannabis use doesn't seem to have been taken into account. Intuitively, it would seem that taking a single bong hit vs. smoking multiple joints in a day would be substantially different, but it seems that the study only asked participants how often they used cannabis as in never/sometimes/daily. It also didn't appear to distinguish between methods of consumption, e.g., vape vs. smoke vs. edible.
The results are concerning, certainly, for cannabis users, especially among older users who are the biggest growth group in terms of cannabis use, I believe, and I wondered if any MeFites with greater knowledge of the topic could note the real-world significance and/or flaws in this study. Thanks.
Best answer: They treated the fraction of days consuming cannabis in the last 30 as a continuous variable, by the way. The tables split into three groups, but the analysis didn't, to my understanding--there are some dose-response charts in the middle. (IIRC, there's a footnote saying that they end up comparing daily use to no use in the first table, which is the one that treats cannabis use as a binary.)
My initial read was that method or quantity per session of consumption wasn't going to be relevant to the conclusion--the survey has 400k responses. However, when you get down to the "never smoked tobacco" cohort, it turns out not that many people use cannabis daily, so maybe there's room for method of consumption to correlate strongly with daily use and that's somehow a confounding effect.
tl;dr cannabis doesn't appear to be good for your heart. The authors do not really speak to the degree of "not good" to any degree of precision (even if that's arguably what an odds ratio gives you). Nor do they make any claim as to the mechanism of harm, beyond observing that inhaling particulate matter (eg by smoking) generally isn't good for you. There's maybe an unstated presumption that people are generally smoking cannabis because cannabis users skew heaving towards people who use(d) tobacco. (And, at least among people I know, smoking was the primary means of consumption pre-legalisation, but post-legalisation. However, I know vanishingly few people my age (elder millennial) who have smoked tobacco.)
Disclaimer: not a doctor; I know shockingly little about statistics proper (the hazards of being a math major) but I do understand logistic regression.
posted by hoyland at 6:34 PM on April 13 [2 favorites]
My initial read was that method or quantity per session of consumption wasn't going to be relevant to the conclusion--the survey has 400k responses. However, when you get down to the "never smoked tobacco" cohort, it turns out not that many people use cannabis daily, so maybe there's room for method of consumption to correlate strongly with daily use and that's somehow a confounding effect.
tl;dr cannabis doesn't appear to be good for your heart. The authors do not really speak to the degree of "not good" to any degree of precision (even if that's arguably what an odds ratio gives you). Nor do they make any claim as to the mechanism of harm, beyond observing that inhaling particulate matter (eg by smoking) generally isn't good for you. There's maybe an unstated presumption that people are generally smoking cannabis because cannabis users skew heaving towards people who use(d) tobacco. (And, at least among people I know, smoking was the primary means of consumption pre-legalisation, but post-legalisation. However, I know vanishingly few people my age (elder millennial) who have smoked tobacco.)
Disclaimer: not a doctor; I know shockingly little about statistics proper (the hazards of being a math major) but I do understand logistic regression.
posted by hoyland at 6:34 PM on April 13 [2 favorites]
Best answer: Hello, I am not a doctor, but I read a lot of studies for fun.
What I'm getting from this study is that they asked a bunch of people about their health and lifestyles, including "Do you smoke tobacco?" and "Do you use cannabis?" and, when they compared people with similar health status and behaviors, they found a higher rate of cardiovascular problems in people who used cannabis more.
They compared people who were tobacco smokers and people who had never smoked tobacco, and among both groups, there was a higher rate of cardiovascular problems among people who used cannabis at all. So, the tobacco smokers who also use cannabis were at a higher risk, and the nonsmokers who used cannabis were at a higher risk. They also looked at weight, age, gender, and other health circumstances. The data suggests that cannabis use is a risk factor for cardiovascular problems regardless of your other health-related behaviors.
Note that this is a self-reported study, and they didn't describe how the survey was completed. Depending on who is asking and how, that can change the answers. For example, if you ask about drugs, the people who are answering have to be convinced they won't get in trouble if they admit to using drugs in the last 30 days. They also have to remember accurately how much they used in the last 30 days, and we all know how that goes-- I can barely remember what I had for lunch yesterday. It is a very large survey, however, so that evens out some of those distortions.
They didn't really distinguish between forms of tobacco or cannabis use and heart problems-- that would be a different study. They also didn't ask people how much they used in a day, just whether they had used during each day in the last 30 days-- whether the amount you use matters would also be a different study. This study is basically looking at existing, very general survey results, and checking to see if they can find a statistical relationship between cannabis and heart problems, which they did (it's probably bad for you.)
posted by blnkfrnk at 6:54 PM on April 13 [7 favorites]
What I'm getting from this study is that they asked a bunch of people about their health and lifestyles, including "Do you smoke tobacco?" and "Do you use cannabis?" and, when they compared people with similar health status and behaviors, they found a higher rate of cardiovascular problems in people who used cannabis more.
They compared people who were tobacco smokers and people who had never smoked tobacco, and among both groups, there was a higher rate of cardiovascular problems among people who used cannabis at all. So, the tobacco smokers who also use cannabis were at a higher risk, and the nonsmokers who used cannabis were at a higher risk. They also looked at weight, age, gender, and other health circumstances. The data suggests that cannabis use is a risk factor for cardiovascular problems regardless of your other health-related behaviors.
Note that this is a self-reported study, and they didn't describe how the survey was completed. Depending on who is asking and how, that can change the answers. For example, if you ask about drugs, the people who are answering have to be convinced they won't get in trouble if they admit to using drugs in the last 30 days. They also have to remember accurately how much they used in the last 30 days, and we all know how that goes-- I can barely remember what I had for lunch yesterday. It is a very large survey, however, so that evens out some of those distortions.
They didn't really distinguish between forms of tobacco or cannabis use and heart problems-- that would be a different study. They also didn't ask people how much they used in a day, just whether they had used during each day in the last 30 days-- whether the amount you use matters would also be a different study. This study is basically looking at existing, very general survey results, and checking to see if they can find a statistical relationship between cannabis and heart problems, which they did (it's probably bad for you.)
posted by blnkfrnk at 6:54 PM on April 13 [7 favorites]
Include me amongst those disappointed to see that the survey questions made no distinction between smoking cannabis and eating it; the only cannabis-related question in the survey was
My current working assumption is that smoking anything is going to be bad for me because it's smoke. It seems completely obvious that exposing the insides of my lungs to gunk that's going to stick to them cannot be conducive to good health. So given that the method of ingestion is such an obvious confounder to control for if what you're trying to assess is risks associated with cannabis per se, this study's failure to do that is kind of weird.
posted by flabdablet at 7:17 PM on April 13 [3 favorites]
During the past 30 days, on how many days did you use marijuana or hashish?(emphasis mine).
My current working assumption is that smoking anything is going to be bad for me because it's smoke. It seems completely obvious that exposing the insides of my lungs to gunk that's going to stick to them cannot be conducive to good health. So given that the method of ingestion is such an obvious confounder to control for if what you're trying to assess is risks associated with cannabis per se, this study's failure to do that is kind of weird.
posted by flabdablet at 7:17 PM on April 13 [3 favorites]
Yeah, I saw a recent one that showed higher heart rate with people smoking vs using edibles. However it’s known to change blood flow in the brain. As well, anyone taking heart medications might find it affects them. Anecdotally, I saw a discussion among Apple Watch users who reported higher resting heart rates (even when they’re fit) for some time after using MJ.
posted by cotton dress sock at 7:38 PM on April 13
posted by cotton dress sock at 7:38 PM on April 13
So given that the method of ingestion is such an obvious confounder to control for if what you're trying to assess is risks associated with cannabis per se, this study's failure to do that is kind of weird.
It's a retrospective analysis of results from some government(?) survey. The advantage is that you get a large dataset. The downside is you only have the questions that were included. I would hazard that the purpose of this article is to say "hey, we should probably study this more and maybe ask things like method or quantity of consumption".
posted by hoyland at 8:34 PM on April 13 [8 favorites]
It's a retrospective analysis of results from some government(?) survey. The advantage is that you get a large dataset. The downside is you only have the questions that were included. I would hazard that the purpose of this article is to say "hey, we should probably study this more and maybe ask things like method or quantity of consumption".
posted by hoyland at 8:34 PM on April 13 [8 favorites]
In the introduction (2nd para), they discuss how cannabis might be associated with heart disease (but unrelated to smoking):
"There are reasons to believe that cannabis use is associated with atherosclerotic heart disease. Endocannabinoid receptors are ubiquitous throughout the cardiovascular system. Tetrahydrocannabinol, the active component of cannabis, has hemodynamic effects and may result in syncope, stroke, and myocardial infarction."
They go on to say:
"Smoking, the predominant method of cannabis use, may pose additional cardiovascular risks as a result of inhalation of particulate matter."
i.e., the former (cannabis use) is independent of the latter (smoking it, which may make the association worse).
posted by lulu68 at 11:49 PM on April 13 [1 favorite]
"There are reasons to believe that cannabis use is associated with atherosclerotic heart disease. Endocannabinoid receptors are ubiquitous throughout the cardiovascular system. Tetrahydrocannabinol, the active component of cannabis, has hemodynamic effects and may result in syncope, stroke, and myocardial infarction."
They go on to say:
"Smoking, the predominant method of cannabis use, may pose additional cardiovascular risks as a result of inhalation of particulate matter."
i.e., the former (cannabis use) is independent of the latter (smoking it, which may make the association worse).
posted by lulu68 at 11:49 PM on April 13 [1 favorite]
We excluded adults >74 years old because cannabis use is uncommon in this population.
Hmmm....I guess I know different elders.
Anyway, I am also not a doctor or medical expert but I also find the method a little wonky, though fair if the goal is just to suggest "we should probably study this more." (Another reason to change how the drug is scheduled in the US to make it easier to study.) In addition to not distinguishing between one and multiple times of ingestion in a given day, or how it's consumed, it also doesn't distinguish between how strong the strains are, or what their THC:CBD ratio is. The THC:CBD ratio is also potentially relevant, and there has been some research that CBD balances a lot of the potential negative symptoms of THC - but again, more studies are needed.
All that said, weed definitely does raise your heart rate. My parents have a friend with a heart condition and he could not safely consume it - he had a few "minor" heart attacks from doing so in his younger days.
posted by coffeecat at 7:19 AM on April 14 [2 favorites]
Hmmm....I guess I know different elders.
Anyway, I am also not a doctor or medical expert but I also find the method a little wonky, though fair if the goal is just to suggest "we should probably study this more." (Another reason to change how the drug is scheduled in the US to make it easier to study.) In addition to not distinguishing between one and multiple times of ingestion in a given day, or how it's consumed, it also doesn't distinguish between how strong the strains are, or what their THC:CBD ratio is. The THC:CBD ratio is also potentially relevant, and there has been some research that CBD balances a lot of the potential negative symptoms of THC - but again, more studies are needed.
All that said, weed definitely does raise your heart rate. My parents have a friend with a heart condition and he could not safely consume it - he had a few "minor" heart attacks from doing so in his younger days.
posted by coffeecat at 7:19 AM on April 14 [2 favorites]
Best answer: Note that per the study, “The most common form of cannabis consumption was smoking (73.8% of current users).” Given that high percentage, I would say that the study more accurately shows an association between smoking cannabis and adverse cardiovascular outcomes. From this study, I don’t think it’s possible to draw any conclusion at all about any potential association between other methods of consumption and adverse cardiovascular outcomes.
posted by maleficent at 9:23 AM on April 14 [1 favorite]
posted by maleficent at 9:23 AM on April 14 [1 favorite]
o given that the method of ingestion is such an obvious confounder to control for if what you're trying to assess is risks associated with cannabis per se, this study's failure to do that is kind of weird.
This is wrong. The method is the mechanism. It’s post treatment. It is not a confounder. It would be statistical malpractice to include the method of ingestion as a control when the main ‘treatment’ variable is cannabis use. It won’t give you the estimate you are interested in.
posted by MisantropicPainforest at 11:56 AM on April 14 [1 favorite]
This is wrong. The method is the mechanism. It’s post treatment. It is not a confounder. It would be statistical malpractice to include the method of ingestion as a control when the main ‘treatment’ variable is cannabis use. It won’t give you the estimate you are interested in.
posted by MisantropicPainforest at 11:56 AM on April 14 [1 favorite]
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posted by a feather in amber at 6:32 PM on April 13