The use of four substances, including cannabis, may increase the risk of developing atrial fibrillation, a very common and potentially serious form of cardiac arrhythmia, a new U.S. study warns.
The other three substances are cocaine, opioids and methamphetamines. Cannabis, however, is a bit particular, because it's a product that is legal and can be easily procured.
"It's interesting that cannabis is being added to the list of risk factors for atrial fibrillation," said Dr. Alexandre Raymond-Paquin, a specialist in electrophysiology and heart conditions at the Montreal Heart Institute.
"We already had smaller, less robust studies that suggested such an association, so I'm not completely surprised, but I'm glad to see that we can finally establish a slightly stronger association between cannabis use and atrial fibrillation," he said.
Researchers at the University of California, San Francisco analyzed data from 23.5 million California adults who required hospital care between 2005 and 2015. None had atrial fibrillation (a disruption of electrical activity in the atria) at the start of the study.
About 133,000 were cannabis users, 98,000 were methamphetamine users, 49,000 were cocaine users, and 10,000 were opioid users.
At the end of 10 years, just under 1 million patients, or 4.2 per cent of the total, had atrial fibrillation. The strongest association was found with methamphetamines and the weakest with cannabis. The risk of developing this form of arrhythmia was still 35 per cent higher among cannabis users.
HARMLESS SUBSTANCE OR NOT
In the collective imagination, cannabis is often seen as being a more banal and harmless substance than cocaine, opioids and methamphetamines. However, Dr. Raymond-Paquin points out that cannabis comes with "potentially harmful cardiovascular effects" that people need to be aware of.
"It's not because it is legal that it is good for your health," he said, drawing a comparison with tobacco. "Just because it comes from a plant doesn't mean it's good for you," he said.
Beyond the increased risk of atrial fibrillation mentioned in this study, other research has associated cannabis with a higher risk of stroke, heart attack and heart failure, he added, but more studies are needed to investigate it further.
The mechanisms by which each substance might increase the risk of atrial fibrillation remain unclear. However, Dr. Raymond-Paquin said, cannabis is known to act on several receptors, including the nervous system, the cardiovascular system and the heart muscle, which may cause some "dysregulation."
"But I have to say that this is an evolving science, and then probably we'll have more answers in the near future," he said.
Atrial fibrillation is the most common form of arrhythmia. It affects 2 per cent of the general population, 4 per cent of those 65 and older, and 12 per cent of those 80 and older. It can lead to stroke if not properly managed.
While some risk factors such as age, gender, and genetic makeup can't be modified, others such as high blood pressure, obesity, sedentary lifestyle, and alcohol consumption can be acted upon, and cannabis use could be added to that list, Raymond-Paquin concluded.
"It's by trying to control all these risk factors, that we can stack the odds in our favour," he said.
The findings were published in the European Heart Journal.
This report was first published by The Canadian Press in French, on Nov. 9. 2022.
