Cannabis Use Was Linked to Lower In-Hospital Mortality After Heart Attack

A large U.S. hospital-records study found that patients with a documented history of cannabis use had lower in-hospital mortality after an acute myocardial infarction (AMI) than comparable patients without such a history. The finding, described by the researchers as a “cannabis paradox,” does not show that cannabis protects the heart or that people should use it after a heart attack.

The 2024 study published in Archives of Medical Science – Atherosclerotic Diseases examined 9,930,007 AMI admissions recorded in the U.S. National Inpatient Sample between 2001 and 2020. The database, maintained through the Agency for Healthcare Research and Quality’s Healthcare Cost and Utilization Project, captures hospital discharge data from across the country and represents more than 97% of discharges from U.S. community hospitals.

Among the admissions analyzed, 117,641—about 1.2%—included a diagnosis or record indicating cannabis use. These patients were substantially younger than those without documented cannabis use, with a mean age of 51.0 years compared with 62.7 years. They were also more likely to be male and to have documented tobacco and alcohol use. By contrast, the non-cannabis group had higher rates of several traditional cardiovascular risk factors, including hypertension, diabetes, chronic kidney disease, peripheral vascular disease and prior coronary artery bypass surgery.

Before statistical matching, the cannabis-use group had a lower in-hospital death rate: 1.8% compared with 4.3% among non-users. After propensity-score matching produced two groups with broadly similar characteristics, mortality remained lower among patients with documented cannabis use—1.8% versus 2.8%.

Further adjustment found that cannabis use was associated with lower odds of in-hospital death, cardiogenic shock, acute ischemic stroke, cardiac arrest, ventricular fibrillation, intra-aortic balloon-pump use and percutaneous coronary intervention (PCI). The adjusted odds ratio for mortality was 0.64. Cannabis use was also associated with lower odds of atrial fibrillation, but higher odds of supraventricular tachycardia, ventricular tachycardia and acute kidney injury. In the matched analysis, coronary artery bypass grafting was slightly more common among cannabis users.

The PCI result requires particular care. A lower rate of PCI does not necessarily mean a milder heart attack or better treatment. It may indicate that the underlying mechanism of the infarction differed between groups. The researchers proposed that some cannabis-associated heart attacks could involve temporary oxygen-supply-and-demand problems, coronary spasm or other non-atherosclerotic mechanisms rather than a ruptured plaque blocking a coronary artery. That explanation remains hypothetical and was not directly tested by the hospital-records analysis.

The study also cannot establish that cannabis caused the better outcomes. The National Inpatient Sample is an observational database based largely on diagnosis and procedure codes. It does not reliably record the amount, timing, frequency or method of cannabis use, and a coded history of use does not necessarily indicate recent consumption. Cannabis use may also have been underreported, while coding errors and unmeasured differences in treatment, disease severity or access to care could have affected the results.

The authors discussed a possible biological explanation involving cannabinoid receptor type 2, or CB2. Some animal and laboratory studies suggest that activating this receptor may reduce inflammation and limit injury during ischemia-reperfusion. These findings are preliminary, however, and do not demonstrate a cardioprotective effect in humans.

The results should also be viewed alongside broader cardiovascular evidence. The American Heart Association’s scientific statement on cannabis and cardiovascular health concluded that available research does not establish cardiovascular benefits and has raised concerns about links between cannabis and heart attacks, arrhythmias and other vascular problems. The Centers for Disease Control and Prevention notes that cannabis can temporarily increase heart rate and blood pressure and may be associated with a higher risk of cardiovascular disease and stroke.

In other words, the study describes an unexpected association among people already hospitalized with AMI; it does not overturn evidence that cannabis may contribute to cardiovascular risk. The lower mortality observed in this dataset may reflect differences in age, comorbidities, the type of infarction, patterns of healthcare use or factors that researchers could not measure.

More detailed studies are needed to determine whether outcomes differ according to cannabis dose, formulation, route of administration, timing of use and the presence of tobacco or other substances. Until then, the “cannabis paradox” is best understood as a signal for further research—not evidence that cannabis improves recovery after a heart attack.