Cannabis, Fatal Heart Attacks, and Flawed Research

There is a recent study on cannabis and heart attacks is making the rounds – some are claiming that the research proves that using cannabis reduces the risk of a fatal heart attack.  But a closer look at the study raises more questions than it answers.  The bottom line is that this was not a well designed study, and drawing firm conclusions from it is a mistake.

Weird Details

The first thing worth mentioning is that the cannabis-using patients who had heart attacks were ten years younger (on average) than the heart attack patients who did not use cannabis.

We know that in general, younger people are more likely to survive any major stress than older people. So we need to question the idea that cannabis is the causal factor – it could be age.

This also raises the question of why the cannabis heart attackers were 10 years younger than their counterparts. It might be random sampling error – but if so, that degree of randomness calls the entire study into question. And if it wasn’t sampling error, what caused the difference?

The second thing worth mentioning is that the cannabis users had lower levels of coronary artery disease… yet they were still getting heart attacks at an earlier age!

Those two findings could be used to paint a very different picture:  “cannabis leads to earlier heart attacks, even in people who don’t have clogged arteries.”  I am not saying that this is an accurate picture of the way things really are, but it is a picture consistent with the study.

Interventional Studies

The research was not an “interventional study” that would be best for determining whether cannabis increases or decreases risk for heart attacks.

An interventional study would involve getting a large number of people, dividing them into 2 groups,  and then giving one group a regular dose of cannabis, while tracking their heart health over time. That type of study would make sure that each group was similar based on age, diet, tobacco use, exercise habits, etc  so that the effects of these other variables were controlled and mostly zeroed out. If an interventional study like that had several thousands of volunteers who were tracked for several years or a decade, we could get a pretty good idea if cannabis use affected heart attacks in one way or the other.

But that kind of study cannot be done today due to legal and organizational hurdles in the United States. So the researchers instead sought out people who already had heart attacks, and worked backwards by asking them questions and testing their blood for cannabinoids.  This is an observational study  – they approach reveals important patterns, but it is much trickier and more likely to lead to wrong conclusions.

The Cannabis/Exercise Analogy

My personal view is that cannabis use may be similar to exercise when it comes to the heart.  Both exercise and cannabis raise the heart rate and blood pressure in the short term, but in the long term, there can be a training effect, where the total risk is lower in people who exercise or use cannabis.

There is some preliminary research that suggests that the risk of heart attack goes up for a few hours immediately after consuming cannabis.  There is also plenty of evidence that the risk of heart attack goes up during and right after strenuous work or exercise.

This analogy suggests that just as there are reasons to avoid exercising too hard or too often, there could be real reasons to take it nice and easy with cannabis. More is not always better.

When we talk about alcohol, it is not really controversial to suggest that drinking in moderation might come with some health benefits, but that excessive drinking can impair health. But some cannabis users and advocates seem unwilling to consider that cannabis might be a tool that can be used improperly.