As cannabis becomes more widely used with increasing legalization, new research raises concerns about its potential impact on heart health.

Two recent studies suggest that cannabis users may have a significantly higher risk of heart attacks – even among young, otherwise healthy individuals.

The findings, based on a large-scale retrospective study and a meta-analysis of past research, highlight potential cardiovascular risks that warrant further investigation.

The research team analyzed data from millions of individuals and found that cannabis users under 50 were more than six times as likely to experience a heart attack compared to non-users.

The second study, which reviewed data from 12 previously published studies, confirmed an elevated risk – showing that cannabis use was linked to a 50% increase in heart attack likelihood.

“Asking about cannabis use should be part of clinicians’ workup to understand patients’ overall cardiovascular risk, similar to asking about smoking cigarettes,” said Dr. Ibrahim Kamel, a clinical instructor at the Boston University Chobanian & Avedisian School of Medicine.

“At a policy level, a fair warning should be made so that the people who are consuming cannabis know that there are risks.”

For the retrospective study, researchers examined data from TriNetX, a global health research network that compiles electronic medical records.

During a median follow-up period of over three years, cannabis users were at much greater cardiovascular risk.

They were over six times more likely to have a heart attack, four times more likely to have an ischemic stroke, twice more likely to have heart failure, and three times more likely to have cardiovascular death, a heart attack, or stroke.

The participants in the study were all below 50 and free from significant cardiovascular disease at the beginning of the study.

Their blood pressure, cholesterol levels and risk of diabetes were normal, and none of them were tobacco smokers or had a history of coronary artery disease.

The second study combined data from 12 earlier studies, examining data from more than 75 million individuals.

Most of these studies were carried out in the United States, with some further research in Canada and India.

Although not all studies included participant age data, those that did indicated an average age of 41.

Of the 12 studies, seven reported a strong association between cannabis use and heart attacks, four reported no significant association, and one reported a weak negative association.

By pooling the data, the researchers established a strong positive correlation – active cannabis users were 1.5 times more likely to have a heart attack than non-users.

Although the studies point to a connection between cannabis and heart health risks, they have limitations.

The experts noted that cannabis use is often linked with other substances, such as tobacco, cocaine, or other illicit drugs, which could also impact cardiovascular risk.

“We should have some caution in interpreting the findings in that cannabis consumption is usually associated with other substances such as cocaine or other illicit drugs that are not accounted for,” said Dr. Kamel.

“Patients should be forthcoming with their doctors and remember that we are their number one advocate and having the full story matters.”

The exact reason why marijuana smoking may increase the risk of heart attacks remains unclear, but researchers have proposed several theories.

Cannabis use may influence the regulation heart rhythm, elevate oxygen demand in the heart muscle, and be a factor in endothelial dysfunction, which would make it more difficult for arteries to relax and dilate.

One of the meta-analysis studies reported that the threat of heart attack reached its peak around one hour following marijuana consumption.

Since both studies were limited by their retrospective design, the researchers believe more studies are needed.

Prospective studies could provide better insight into which groups face the highest risks and how cannabis interacts with other cardiovascular factors.

Previous research presented at the American College of Cardiology’s Annual Scientific Session in 2023 also linked daily marijuana use with an increased risk of coronary artery disease.

With cannabis use becoming more common, especially in regions where it is legal, understanding its potential risks remains a priority for public health.

The retrospective study is published in the journal JACC Advances.

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