Cannabis use linked to higher risk of intraoperative and postoperative heart attack, according to study promoted by ASA

A new study finds that patients who use cannabis may face a significantly higher risk of heart attack during and after surgery, while also unexpectedly showing a lower risk of blood clots in the veins.

The American Society of Anesthesiologists (ASA) has promoted the study, which was presented this week at its ANESTHESIOLOGY 2026 annual meeting.

Some notes about the study from ASA:

• “Cannabis use among surgical patients nearly tripled over the past decade, yet many patients still do not disclose their marijuana use to their surgeon or anesthesiologist.”
• “Cannabis users had a 46% higher risk of heart attack during or shortly after surgery compared to non-users, according to an analysis of more than 44,000 patients.”
• “Cannabis users had a 22% lower risk of venous thromboembolism…The authors emphasize this finding warrants further investigation and does not establish that cannabis has a protective effect.”
• The researchers found “no significant links between cannabis use and stroke, respiratory failure, acute kidney injury or death.”

“Our findings show that it is vitally important to tell your anesthesiologist before your procedure if you use marijuana, whether for medical or recreational purposes,” stated the study’s lead author, Nader D. Nader, MD, Ph.D., FASA, professor of anesthesiology and surgery at the Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, New York. “This is not about judgment; it is about safety. Cannabis can affect your heart, your blood vessels and how your body responds to anesthesia. Knowing about a patient’s cannabis use allows the anesthesiologist to take extra precautions to keep patients safe during and after surgery.”

“Today’s cannabis products are far more potent than they were decades ago, and higher THC levels can have serious cardiovascular effects,” added study co-author Rose Berkun, MD, FASA, associate professor of anesthesiology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, New York. “Educating patients about these risks and encouraging them to disclose cannabis use to both their surgeon and anesthesiologist before surgery are important steps in helping to provide the safest possible care.”

Read ASA’s full press release about the study here.