Cannabis use increases risk of heart attack in young people

Marijuana is now legal in many countries, but is it safe? Two new studies add to the list of evidence that people who use marijuana are more likely to suffer heart attacks than those who don’t use the drug, even among young and otherwise healthy adults. The results of the retrospective study involving more than 4.6 million people are published in the journal JACC Advances, and a meta-analysis of 12 previously published studies is presented at the annual scientific session of the American College of Cardiology (ACC.25).

Marijuana use has increased in the United States, especially in states where it is legal to buy, sell and use the drug for recreational purposes. In a retrospective study, researchers found that marijuana users under the age of 50 were six times more likely to have a heart attack than those who did not use marijuana. The meta-analysis, which is the largest pooled study to date on heart attacks and cannabis use, found that those who used the drug had a 50 percent increased risk.

The question about cannabis use should be part of patient screening to determine overall cardiovascular risk, just like the question about smoking cigarettes. There should be a fair warning at the policy level so that people who use cannabis know that there are risks.”

 Ibrahim Kamel, physician, clinical instructor at Boston University School of Medicine, internal medicine resident at St. Elizabeth’s Medical Center in Boston and lead author of the study

Kamel and his team conducted a retrospective study using data from TriNetX, a global health research network that provides access to electronic medical records. The results of the study showed that over an average of three years of follow-up, cannabis users had more than six times the risk of heart attack, four times the risk of ischemic stroke, two times the risk of heart failure and three times the risk of death from cardiovascular disease, heart attack or stroke. All study participants were younger than 50 years of age and had no major cardiovascular comorbidities at baseline, their blood pressure and low-density lipoprotein (LDL) cholesterol levels were within normal limits, and they did not have diabetes, smoking, or prior coronary artery disease.

For the meta-analysis, the researchers combined data from 12 previously published studies that collectively included more than 75 million people. The studies were rated as moderate to good quality in terms of methodology. Of the 12 studies, 10 were conducted in the United States, one in Canada and one in India. Some studies did not include information on the age of participants, but the average age of participants was 41 years, suggesting that the pooled sample reflects a relatively young population.

Individually, seven studies found a significant positive association between cannabis use and heart attack rates, while four studies found no significant difference and one showed a nonsignificant negative association. When the researchers combined the data from all the studies and analyzed them together, they found a significant positive association: active cannabis users were 1.5 times more likely to have a heart attack compared to those who were not current cannabis users.

Cannabis use and heart attack rates were assessed similarly across studies. However, due to inconsistencies in the data from each study, the researchers were unable to account for a number of potential contributing factors, including the duration and amount of cannabis use, as well as the use of tobacco and other drugs.

Some caution should be exercised in interpreting the findings, as cannabis use is usually associated with other substances, such as cocaine or other illicit drugs, that are not accounted for.

Although the mechanisms by which marijuana or its components affect the cardiovascular system are not fully understood, researchers speculate that it may affect heart rate regulation, increase the heart muscle’s need for oxygen, and contribute to endothelial dysfunction, which makes it harder for blood vessels to relax and dilate, which can impair blood flow. One study included in the meta-analysis found that the risk of heart attack peaks about an hour after marijuana use.