Medical Cannabis Use for Chronic Pain Linked with Increased Afib Risk

The study found that risk of new-onset arrhythmia, which included conditions like atrial fibrillation, flutter, and paroxysmal tachycardia, was doubled in those who used medical cannabis to manage chronic pain compared to a control group.

Holt and his team utilized health data from national Danish health registries to investigate the link between medical cannabis and arrhythmia. Medical cannabis is not formally approved for chronic pain management in Denmark, but a government program has allowed physicians to prescribe it for that reason.

Researchers looked at data from more than 1.8 million patients with chronic pain.

Out of that group, only a very small number of patients received medical cannabis: about 5,000 people.

The group of medical cannabis users were matched 1:5 with 27,000 patients that had similar characteristics, including age, sex, and use of other pain medications.

In large, population-based studies like this, it is impossible to remove all confounding factors, but the goal is to remove as many as possible.

Patients in the study did not have a history of arrhythmia, nor had they previously been prescribed medical cannabis.

Over a 180-day follow-up period, 42 patients who used medical cannabis developed an arrhythmia; in three-out-of-four cases, it was atrial fibrillation.

Overall 0.8% of medical cannabis patients experienced an arrhythmia compared to 0.4% in the control group. The risk was greatest in patients with cancer and cardiometabolic conditions like diabetes.

No association was found between medical cannabis and acute coronary syndrome.

“These findings should spur further investigations into the viable use of cannabis treatment for chronic pain and particularly into possible side effects. It should be paramount to physicians that the ongoing legalization of cannabis meant for therapeutic use is kept purely scientific and not political,” said Holt.

Although the study demonstrates an increase in risk, questions remain about how this risk should factor into patient care.

“You need to distinguish statistical significance from clinical significance,” said Dr. Rod Passman, MD, a Professor of Medicine and Director of the Center for Arrhythmia Research at Northwestern University. Passman wasn’t affiliated with the study.

“If you tell someone their risk is double, that’s really important. But if you tell someone their risk goes from 0.4% to 0.8%, most of us would not believe that that is a major increase in risk that would impact clinical decision making like whether I would take a medication or not,” he said.

He notes that many pain medications, even over-the-counter nonsteroidal (NSAID) medications like ibuprofen, are associated with arrhythmia.

Opioids, pervasive and powerful pain medicines like morphine, codeine, and fentanyl, are too.

A 2018 review found that even at low doses could increase the risk of arrhythmia.

Patients and healthcare professionals will always need to assess risks and benefits when assessing treatment needs.

“I don’t think that I would take someone who was in chronic pain, which failed typical therapies, and prevent them from getting medical marijuana because of the potential risk of exacerbating their atrial fibrillation when that risk is going to be relatively low,” he said.

Both Passman and Holt acknowledge that good data on medical cannabis is sorely lacking. Prior research has tended to focus on recreational cannabis usage. With the rise of legalization in Europe and the United States, use of medical cannabis is steadily increasing.

“This is of increasing interest given the increasing use of cannabis, both for medical and recreational purposes…Often there’s a lot of problems with these studies because, historically, this has been an illegal medication. So we don’t have a lot of good, solid data on it,” said Passman.

“Prescribed medical treatment must be founded on sufficient evidence of effect, including considerable knowledge on side-effects which this study adds a sliver of, but more is certainly needed,” said Holt.

The American Heart Association has stated that there are “no cardiovascular benefits” to using cannabis, either recreationally or medicinally. In a scientific statement on cannabis and cardiovascular health issued in 2020, the AHA points out that in a variety of studies, cannabis consumption has been associated with atrial fibrillation and cardiovascular disease. They too, acknowledge a need for more and higher quality data and that there is “an urgent need for carefully designed, prospective short- and long-term studies.”

AHA spokesperson Robert L. Page II, PharmD, a Professor at the University of Colorado and Chair of the AHA’s 2020 scientific statement on cannabis, told Healthline that the Danish research “absolutely” aligns with the AHA’s statement.

“I treat cannabis use (particularly when vaped or smoked) as a potential risk factor for heart disease, which is why I do not recommend smoking or vaping any form of cannabis. Thus, medical providers should be screening for underlying cardiovascular risk factors or underlying conditions that could contribute to a heart attack, stroke or heart rhythm disturbance in anyone who uses cannabis,” he said.

A European study found that patients with chronic pain who used medical cannabis were more likely to experience heart arrhythmia than a control group.

While the risk of arrhythmia was still low (0.8%) among the medical cannabis group, it was a two-fold increase over the control group (0.4%).

Researchers and organizations, including the American Heart Association, say there is a tremendous need for more studies and high quality data on the association between cannabis and cardiovascular disease.