For the retrospective analysis, the researchers used the TriNetX database, which contains electronic medical records. The study participants had no serious cardiovascular disease at the start of the observations, their cholesterol levels and blood pressure were within normal limits, they did not smoke regular cigarettes and did not have diabetes.
Over a 3-year follow-up period, cannabis users had a four-fold increased risk of ischemic stroke, a two-fold increased risk of heart failure, and a three-fold increased risk of death from cardiovascular disease.
The meta-analysis, which included more than 75 million people, used data from the United States, Canada, and India. Of the 12 studies, 7 found a significant link between cannabis use and heart attack, 4 found no difference, and 1 showed a weak inverse relationship. However, when combining data from all studies, the scientists confirmed a 1.5-fold increased risk of heart attack in active marijuana users.
An analysis of the data found that most studies had similar methods for measuring cannabis use and heart attack. However, the researchers were unable to account for factors such as frequency and volume of use, as well as the influence of other substances, including tobacco and drugs.
Researchers have suggested that marijuana may affect the cardiovascular system in a number of ways. It may disrupt the heart rhythm, increase the heart muscle's need for oxygen, and impair the tone and dilation of blood vessels, which may lead to blockage.
One study found that the risk of heart attack increases within the first hour of using marijuana.
The work's shortcomings are related to the retrospective nature of the data. Scientists believe that additional studies will help identify the groups at greatest risk. In 2023, American cardiologists already provided data confirming the link between daily marijuana use and an increased risk of coronary heart disease.
The study's findings are published in the journal JACC Advances. They will also be presented at the annual meeting of the American College of Cardiology (ACC.25). Doctors are calling for cannabis use to be taken into account when assessing cardiovascular risk, as is already done with cigarette smoking. The authors of the study believe that people should be aware of the possible risks.