Study: Cannabis Doesn’t Increase Heart Attack Risk

Middle-aged adults with a history of cannabis use over the previous year did not have a higher risk of suffering a heart attack, according to the results of a recent study by researchers at the University of California in San Diego.

The new study, “Associations Between Monthly Cannabis Use and Myocardial Infarction in Middle-Aged Adults: NHANES 2009 to 2018,” was published on August 7 in the peer-reviewed American Journal of Cardiology, found that a history of cannabis use over the previous year was not associated with an elevated risk of myocardial infarction (MI) among a nationally representative study of nearly 10,000 adults aged 35 to 59. Additionally, study participants who reported using cannabis in the month before experiencing an MI, also commonly known as a heart attack, showed a lower risk compared to participants who had not used cannabis recently.

“In a representative sample of middle-aged US adults, a history of monthly cannabis use for more than a year before a myocardial infarction was not linked to a subsequent physician-diagnosed MI, after accounting for cardiovascular risk factors,” the authors of the study wrote. “However, when considering recent use, the odds were three times greater if no use was reported in the past month.”

Study Included Nearly 10,000 Participants

To conduct the study, the researchers performed an analysis of data from the National Health and Nutrition Examination Survey (NHANES), a series of studies designed to assess the health and nutritional status of adults and children in the United States. The study assessed the relationship between a history of monthly cannabis use preceding an MI in a nationally representative sample of middle-aged adults in the United States.

Among the 9,769 respondents of the survey analyzed for the study, a quarter (24.9%) reported a history of cannabis use for at least one year prior to experiencing a myocardial infarction. A history of MI was reported by 2.1% of all respondents and 3.2% of those who reported a history of monthly use. Additionally, 1.5% of respondents reported that they had never used cannabis, and 2.2% denied a history of being a monthly user.

The study found that subjects who had used cannabis at least monthly over the past year did not show a higher risk of having a heart attack compared to non-users when potential confounding factors such as physical activity, body mass index and the use of alcohol or cigarettes were adjusted for. However, when stratified by recent use, the odds of MI were three times greater when no cannabis use was reported within the past month than when use was reported in the month preceding a heart attack.

The study also found that the duration of monthly cannabis use by survey respondents was not significantly associated with myocardial infarction, with those who had used cannabis on a monthly basis for more than 10 years showing similar rates of incidence compared to users with a shorter history of monthly use.

“The length of monthly use before the MI, including use >10 years, also showed no association. The evidence base for cardiovascular harms is conflicting and limited by the ability to accurately quantify use, especially the method of use, dose, and potency,” the researchers wrote. “Given the expanding access to cannabis products in the United States and around the world, more research, particularly longitudinal and experimental studies, is needed.”

In a separate finding that the researchers who conducted the study characterized as “unexpected,” subjects who had recently stopped using marijuana showed an increased risk of experiencing a heart attack.

Study Inconsistent with Earlier Research

The researchers noted that the results of the study diverge from previous research in the Behavioral Risk Factor Surveillance System survey in US adults, which reported elevated odds of MI among young adults 18 to 44 years old, and a separate study that reported increased odds of MI or coronary artery disease (CAD) among adults 18 to 74 years old who did not smoke cigarettes.

Other studies have shown an apparent link between cannabis use and “an increased risk of cardiovascular diseases, as well as heart attacks and strokes,” according to a health warning from the American Heart Association earlier this year. In the warning, which was published in time for the 4/20 festivities in April, the cardiovascular health advocacy organization noted that a 2020 scientific statement from the group maintained “that while marijuana, also known as cannabis, may be helpful for some other medical conditions, it does not appear to have any well-documented benefits for the prevention or treatment of cardiovascular diseases (CVD).”

Robert L. Page II, a professor in the Department of Clinical Pharmacy and the Department of Physical Medicine/Rehabilitation at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences in Aurora, Colorado, noted that “the way cannabis is consumed may make a difference in how it affects the heart and blood vessels. Many people don’t realize that cannabis smoke contains components similar to tobacco smoke.”

“Smoking and inhaling cannabis, regardless of THC content, has been shown to increase the concentrations of poisonous carbon monoxide and tar in the blood similar to the effects of inhaling the smoke from a tobacco cigarette,” said Page, one of the authors of the American Heart Association’s 2020 statement on medical and recreational marijuana use and cardiovascular disease. “Also, limited information exists on the hazards of exposure to secondhand cannabis smoke.”

However, a 2021 literature review of 67 studies published in the American Journal of Medicine found that “marijuana itself does not appear to be independently associated with excessive cardiovascular risk factors,” although the authors of the review warned that cannabis “can be associated with other unhealthy behaviors such as alcohol use and tobacco smoking that can be detrimental” to cardiovascular health.