Weed and Heart Attacks: What Does the Science Say?

Weed and Heart Attacks: What Does the Science Say?

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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 a potential 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 give our take on whether the results are concerning or not.

We'll also review other medical studies on weed and cardiovascular disease risk and share our thoughts on whether there's a legitimate risk that consumers should be aware of, as well as whether different formats (inhaled vs edible) of cannabis make a difference.

The Study in Question

On September 7th 2021, the Canadian Medical Association Journal (CMAJ) published a medical review on recent cannabis use and myocardial infarction (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 U.S. 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.

Issues With the Study

Population studies mean that researchers look at associations but cannot prove causation. This type of research can be interesting and 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 has a direct, dose-dependent increased risk of heart disease. 17.4% of recent cannabis users from the CMAJ study were 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 medical 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 found no overall proof of harm. There were a few case studies reported which involved young patients who used high doses of cannabis regularly and had an adverse cardiac event.

The paper did suggest 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 support this effect.

One population review did find 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 6 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 the 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 or other stimulants.

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 cannabis itself.

Frequent Cannabis Use Associated With Heart Disease

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).

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Weed may increase the risk of heart disease but we don’t believe that research studies have proven so conclusively. The CMAJ study which gained traction in mainstream media has design flaws in our opinion which make its data less useful. The study failed to account for confounding factors like heavy alcohol use, which were found to be more common in the cannabis users, and which we know can cause heart disease.

We believe that confounding factors like insecticide and pesticide residue on cannabis, as well as the actual act of smoking, may be more likely to cause health issues than the cannabis plant itself, though we hope that future trials evaluate the safety of cannabis in food to better isolate the specific risks of the plant (if any).

It seems logical that cannabis in edible form may be a healthier option than inhaled cannabis smoke, but a recent medical study found that daily cannabis use of any type increased the risk of cardiovascular disease.