Disclaimer: This article doesn’t constitute medical advice and is just the opinion of the writer(s). We recommend that individuals speak with their doctor about cannabis risks.
There have been several articles in the mainstream media recently reporting an association between weed and heart attacks. This is because a large research study was published in 2021 suggesting a link.
But does smoking weed really increase the risk of heart attacks, or is this just fearmongering? What did the study in question actually show? Do other studies on the topic report similar results? And should cannabis users be concerned?
In this article we’ll answer all of these questions and more, as we analyze the medical study in question to report what was found, and to give our take on whether or not the results are concerning.
We'll also review other medical studies on cannabis use and cardiovascular disease risk to see if the results were replicated, as well as whether different formats (inhaled vs edible) of cannabis make a difference health-wise.
The Study in Question
On September 7th 2021, the Canadian Medical Association Journal (CMAJ) published a medical review on recent cannabis use and myocardial infraction (heart attack) risk.
The study found an association between the two: recent cannabis users had a higher risk of heart attack than those who didn't use cannabis.
This study analyzed data from 33,173 US adults.
4,160 (17.5%) of them had recently used cannabis. 1.3% of recent cannabis users experienced a heart attack during the study period, while only 0.8% of non-users did.
We have a number of issues with the conclusions that mainstream media outlets are drawing from this study.
Population studies mean that researchers look at associations but cannot prove causation.
This type of research can provide data that leads to hypotheses to test in future medical studies, but usually shouldn't lead to actionable takeaways because there are so many confounding factors.
As an example, if people who use wheelchairs tend to die much more frequently than those who don’t, this doesn’t infer that wheelchairs cause deaths. It shows that people in poor health tend to be in wheelchairs.
There’s a difference between correlation and causation that many popular health media outlets fail to understand and clearly explain.
We see this issue of confounding factors and lack of causation when we analyze the cannabis study data.
The researchers found that recent cannabis use was more common in males, cigarette users and heavy alcohol drinkers. All three of these population groups have higher independent risk of cardiovascular disease, so it makes sense that the recent cannabis group would show slightly increased risk of cardiovascular disease.
This doesn't prove the risk has anything to do with cannabis consumption.
We know from previous medical research that heavy alcohol use directly increases the risk of heart disease in a dose-dependent manner.
17.4% of recent cannabis users in the CMAJ study were also heavy alcohol users, while only 5.3% of non-cannabis users were.
This difference alone could account for the entire disparity in cardiovascular incidents between cannabis users and non-cannabis users concluded by the study.
What Do Other Studies Say?
There are other clinical studies which have analyzed marijuana use and heart disease risk.
A medical review published in the Missouri Medicine journal analyzed data on cannabis use and cardiovascular risk, and suggested one biological mechanism by which cannabis could contribute to heart disease, which is called platelet aggregation.
High concentrations of cannabinoids (the active chemical compounds in cannabis) may induce platelet aggregation which can block blood flow. This appears to occur due to an inflammatory effect on the arterial wall, but this research is preliminary and much more data is needed to confirm this effect.
One population review found that cannabis use was associated with a higher likelihood of heart issues even when adjusting for tobacco use and alcohol intake.
The research is still too early-stage for us to give a definitive opinion, but it appears that regular marijuana use may slightly worsen cardiovascular health.
A YouTube video published by NutritionFacts.org is under six minutes long and is very engaging and well-produced, and does a deep dive into more of the research on this topic:
Is Smoking the Issue?
Smoking anything is directly harmful to the lungs, because of combustion byproducts.
When plants are heated until they smoke and then inhaled, whether it’s tobacco or cigarettes or any other plant material, it can harm the lungs.
Medical research suggests that vaping, or using vaporized cannabis, is less harmful than smoking cannabis because of the decrease in inhaled toxins.
Another issue is that since cannabis is still illegal in many jurisdictions, consumers can't check the purity of the product they’re smoking.
Unregulated cannabis may have pesticide residue, and also carries the risk of being adulterated or “laced” with more dangerous compounds like PCP.
It’s also well-known that many users consume unhealthy and processed food after cannabis use, because of its effects on appetite.
We believe that these confounding factors, along with lifestyle factors like increased association of heavy alcohol use, may be more likely to be the causes of heart disease risk associated with cannabis use than the plant itself.
Is Frequency the Issue?
A research study published in February of 2023 found that frequent cannabis use is associated with increased risk of heart disease.
The American College of Cardiology reports that daily cannabis users were 34% more likely to have coronary artery disease than non-smokers, but monthly smokers were not at significantly more risk.
The study authors note that THC may promote inflammation and buildup of plaque in arteries, and this study did not differentiate between different types of cannabis consumption (edible versus smoking).
