Nationwide study suggests link between medical cannabis for chronic pain and abnormal heart rhythm

People taking medical cannabis for chronic pain have a slightly increased risk of arrhythmia, according to research published in the European Heart Journal today (Thursday). Arrhythmia is when the heart beats too slowly, too quickly or irregularly. It includes conditions like atrial fibrillation.

Recreational use of cannabis has been linked to cardiovascular disease but there has been very little research on the side effects of medical cannabis.

Researchers say the new study is important as a growing number of countries now permit medical cannabis as a treatment for chronic pain.

The study was led by Dr. Anders Holt from Copenhagen University Hospital – Herlev and Gentofte in Denmark. It included data on 5,391 Danish patients who had been prescribed cannabis for chronic pain. This included people with pain in their muscles, joints or bones, people with cancer and those suffering with nerve pain. Researchers compared this group with 26,941 patients who also had chronic pain but were not receiving cannabis as a treatment.

The data showed that patients receiving medical cannabis had a 0.8% risk of being diagnosed with arrhythmia that required monitoring and possible treatment within 180 days of receiving cannabis. This risk was more than twice the risk for patients with chronic pain who were not taking cannabis. The difference in risk between the two groups had become smaller when researchers looked at the first year of treatment.

Patients taking cannabis who were aged 60 and older and those already diagnosed with cancer or cardiometabolic disease, such as heart disease, stroke and diabetes, had the largest increases in their risk of arrhythmia.

The study did not show any link between taking medical cannabis and the risk of acute coronary syndrome, which includes a heart attack and unstable angina, stroke or heart failure.

Researchers say this is the first nationwide study of its kind investigating the cardiovascular effects of medical cannabis for chronic pain. However, they caution that this is an observational study. Dr. Holt explained: “Despite our best efforts to make a balanced comparison, it can never be assumed that patients prescribed medical cannabis do not differ from patients not prescribed medical cannabis, and this could influence the results.”

Reference: Nationwide study suggests link between medical cannabis for chronic pain and abnormal heart rhythm; European Heart Journal, DOI: 10.1093/eurheartj/ehad834