A new study conducted by researchers at the University of California, San Francisco (UCSF) sheds new light on the long-term consequences of cannabis consumption, revealing significant cardiovascular risks associated with chronic use, whether through smoking or consumption via edibles. The report, published on May 28, 2025, in the journal JAMA Cardiology, highlights that individuals who regularly use marijuana in any form exhibit reduced blood vessel function, comparable to that of tobacco smokers. Specifically, vascular function in cannabis users, regardless of the method of intake, was reduced by approximately half compared to non-users.

Reduced vascular function is a significant risk factor for heart attack, hypertension, and other cardiovascular diseases. This finding raises serious questions about the perception of cannabis as a benign alternative to tobacco, especially given the growing legalization and use of marijuana in many parts of the world.

Methodology and Key Research Findings

The research team recruited 55 apparently healthy individuals between October 2021 and August 2024. Participants were regular marijuana users, either through smoking or consuming edibles containing tetrahydrocannabinol (THC), the main psychoactive compound in cannabis. Importantly, none of the participants used any form of nicotine. The criterion for participation was cannabis consumption at least three times a week for at least one year. The average duration of chronic use for smokers was ten years, while users of edibles had consumed cannabis for an average of five years.

The study found that marijuana smokers, in addition to reduced vascular function, also had changes in their blood serum that are harmful to endothelial cells. Endothelial cells form the inner lining of all blood and lymphatic vessels and play a crucial role in maintaining circulatory health. Interestingly, individuals who consumed THC edibles did not show these specific changes in blood serum, despite also having reduced vascular function. This finding suggests that smoking marijuana negatively affects vascular function through different mechanisms than THC ingestion.

According to the study's lead author, Dr. Leila Mohammadi, and senior author, Dr. Matthew L. Springer, these results indicate that the act of smoking itself and the presence of THC contribute to blood vessel damage in different ways. Although the exact mechanism by which THC damages blood vessels is not yet fully understood, researchers state that it must occur in a way that does not involve the aforementioned changes in blood serum observed in smokers.

Broader Context of Cannabis's Impact on the Heart

This UCSF study adds to a growing body of research indicating the potential adverse effects of cannabis on the cardiovascular system. Some earlier studies have shown a link between marijuana use and an increased risk of heart attack, particularly in younger users. For example, one retrospective study found that cannabis users under the age of 50 had a more than six-fold increased risk of heart attack compared to non-smokers. Another meta-analysis, which included data from multiple studies, showed a 50% higher risk among cannabis users.

Although the mechanisms by which marijuana or its components affect the cardiovascular system are not fully understood, scientists hypothesize that cannabis can affect heart rhythm regulation, increase the heart muscle's demand for oxygen, and contribute to endothelial dysfunction, which hinders normal blood flow. Endothelial dysfunction is considered an early indicator of cardiovascular disease and can lead to the development of atherosclerosis, a condition where plaque builds up inside the arteries.

Research also suggests that smoking cannabis increases the concentration of carbon monoxide and tar in the bloodstream, similar to smoking tobacco, which is associated with heart muscle diseases, chest pain, heart rhythm disorders, and other serious conditions. It has been noted that THC can increase heart rate and blood pressure immediately after consumption.

Differences Between Smoking and Edibles

While cannabis edibles avoid the respiratory risks associated with smoking, such as bronchial and lung irritation and chronic cough, they are not without their own risks. The UCSF study shows that THC edibles also lead to reduced vascular function. It was observed that users of THC edibles experienced a 56 percent reduction in vascular function, while for marijuana smokers, this reduction was 42 percent compared to non-cannabis users. It is important to emphasize that the research showed an association, not necessarily a causal link; that is, it can be stated that cannabis users have poorer vascular function, but not that cannabis use is the direct cause.

Experts warn that the delayed onset and prolonged effects of edibles make precise dosing difficult, which can lead to overdose and serious behavioral problems, including cognitive and motor dysfunction, anxiety, and even transient psychotic symptoms. Some analyses of cannabis-related emergency room admissions have shown that edibles are more likely to lead to acute psychiatric symptoms, intoxication, and cardiovascular symptoms compared to inhaled forms.

It appears that the act of smoking itself, independent of THC, has negative consequences. Experiments on rats exposed to cannabinoid-free marijuana smoke also showed vascular and cardiac damage. This supports the thesis that switching from smoking tobacco to smoking marijuana does not eliminate the cardiovascular risks associated with smoke inhalation.

Implications for Public Health

Given the increasing availability and acceptance of cannabis, the findings of this and similar studies have important implications for public health. Further research is needed to fully understand the long-term effects of different methods of cannabis consumption on cardiovascular health. Clinicians should consider asking about cannabis use as part of assessing patients' overall cardiovascular risk, similar to how they ask about cigarette smoking. Particular attention should be paid to educating the public, especially younger people, about the potential risks associated with regular marijuana use, regardless of the form of consumption. Until more robust data are collected, users are advised to exercise caution and moderation in cannabis use.

Funding for this research was provided by the National Institute on Drug Abuse (NIDA), the California Department of Cannabis Control, the California Tobacco-Related Disease Research Program, the National Heart, Lung, and Blood Institute, and the FDA Center for Tobacco Products. Additional support was provided by the Elfenworks Foundation (in memory of Deb O’Keefe), the Roy E. Thomas Medical Foundation, and the Gootter-Jensen Foundation.

Source: University of California