There’s been much press coverage this year of a scientific study associating cannabis use with heart attack frequency in young adults.
Most popular news sites don’t have doctors or anyone credentialed on staff who can interpret a medical trial, so they just run with the headline even if there may be methodological flaws with the study.
In this article we’ll examine the popular cannabis and heart attack study and explain whether we believe weed usage is likely to increase risk of heart attack in young adults.
The Study in Question
On September 7th 2021, the Canadian Medical Association Journal (CMAJ) published a study 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 the population which didn’t use cannabis.
This study analyzed data of 33,173 U.S. adults. 4,160 of them had recently used cannabis. This is a large population study and the numbers of respondents are definitely high enough to establish statistical significance.
Issues With the Study
Population studies mean that researchers look at associations between behaviors in large populations. 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 most of the popular health media doesn’t understand.
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.
We find it strange that the researchers of the cannabis study didn’t adjust for these risk factors. It’s common practice when running data models to adjust for known risk factors so the final data is more accurate.
Other Studies on Weed and Heart Disease Risk
After reviewing this study, which we believe is somewhat poorly researched and concluded, we were curious about other medical studies which have looked into marijuana use and heart disease risk.
One paper reviewed medical research on the cardiovascular risk of marijuana and found some adverse case studies, but no overall proof of harm. The case studies generally 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. This study is much better designed in our opinion than the recent one making headlines, because it has accounted for other variables which could be increasing cardiovascular risk outside of cannabis.
Cannabidiol, or CBD, has actually been found to improve cardiovascular function in a medical review, which is interesting because CBD is naturally found in cannabis. It decreased blood pressure in stressed patients and decreased organ damage in heart disease models.
Overall we believe the data is too experimental and early-stage to determine whether cannabis truly causes heart disease. There is definitely a need for further research given how many adults use cannabis regularly.
Why We Think Confounding Factors, Not Cannabis, Are Likely The Culprit
Smoking anything is directly harmful to the lungs, because of the combustion byproducts. When plants are heated until they smoke, whether it’s tobacco or cigarettes, they can harm the lungs.
Medical research has proven that vaping, or using vaporized cannabis, is less harmful than smoking cannabis because of the decrease in inhaled toxins.
Since cannabis is still illegal in many jurisdictions, many consumers have no idea about the purity of the product they’re smoking. Unregulated cannabis is likely to 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 the rapid increase in appetite.
We believe that these confounding factors, along with lifestyle factors like increased association of heavy alcohol use, are more likely to be the causes of heart disease risk associated with cannabis use in population studies.