A study of over 44,000 patients found that cannabis use is associated with a higher risk of heart attack during or after surgery, but a lower risk of venous blood clots.

A study presented at the ANESTHESIOLOGY 2026 annual meeting indicates that patients who use cannabis face a 46% higher risk of heart attack during or shortly after surgery. Researchers analyzed data from 44,312 surgical patients to determine the cardiovascular effects of marijuana use. While the risk of heart attack increased, the study also identified a 22% lower risk of venous thromboembolism among cannabis users.

Clinical Implications and Recommendations

Lead author Nader D. Nader, a professor at the Jacobs School of Medicine and Biomedical Sciences, emphasized that patients should disclose their cannabis use to their anesthesiologist. This information allows medical teams to adjust cardiovascular monitoring, anesthetic plans, and the use of blood-thinning medications. Co-author Rose Berkun noted that modern cannabis products often contain higher levels of THC, which can increase heart rate, blood pressure, and the heart's oxygen demand, potentially triggering arterial spasms during the stress of surgery.

Understanding the Findings

Researchers found no significant association between cannabis use and other complications such as stroke, respiratory failure, acute kidney injury, or death. Regarding the lower risk of blood clots, the authors cautioned that this does not prove cannabis has a protective effect. They noted that cannabis interacts with body receptors in complex ways that may influence inflammation and clotting, and further study is required to fully understand these physiological responses.