Cannabis inhalation tied to fewer premature heart beats, not more

Clinical takeaway: In a habitual user, inhaling cannabis may not disturb heart rhythm immediately after use. But this doesn't answer questions around longer-term cardiovascular risks. 

Cannabis legalization has outpaced the cardiac evidence. Now, it is widely legal and used by millions of US adults, plenty of whom take commercial availability as a kind of clearance on health concerns. But much of the cardiovascular evidence around cannabis thus far has been less reassuring. 

Prior work has pointed toward more arrhythmia, mostly from studies that were observational or self-reported. This study randomized use, assigning inhalation or abstinence day by day, with each participant serving as their own control. 

Cannabis days brought 9% fewer ectopic beats than abstinence days, a statistically significant difference. The drop came from premature atrial contractions, down 10%, the measure whose frequency predicts atrial fibrillation better than any other single variable. The effect scaled with exposure: each individual inhalation was tied to a 2% reduction in ectopic beats. Premature ventricular contractions, which carry their own association with heart failure, did not change. 

Other trial endpoints were flat. Step counts, sleep duration, and glucose levels did not differ significantly between cannabis and abstinence days, which the investigators also found unexpected. 

Investigators randomized 108 habitual users with a mean age of 32 and no diagnosed arrhythmia to inhale or abstain on each of 14 days while monitoring rhythm, activity, sleep, and glucose continuously. Adherence was imperfect, which the authors count alongside possible withdrawal effects as a limit on causal reading. 

The tractable next question is mechanistic: what in inhaled cannabis suppresses premature atrial contractions, and whether that pathway can be reached another way. Their day-to-day drivers are barely mapped. Cumulative cardiovascular risk also remains an open question. 

"We were surprised by the results because they contradicted our original hypothesis," said Gregory Marcus, MD, MAS, an endowed professor of atrial fibrillation research in the UCSF Division of Cardiology. "That's why randomized trials are so important. When the data challenge our expectations, our job as scientists is to understand them, not ignore them." 

"This study examined the acute effects of cannabis in people who use it regularly and was not designed to evaluate the long-term health consequences," he added. "The overall health effects of inhaled cannabis may still be net negative, but these findings suggest there may be something about cannabis that can teach us more about the biological mechanisms that produce premature atrial contractions. That knowledge could eventually lead to new approaches for preventing or treating abnormal heart rhythms." 

Source: Elias A, et al. (2026 Aug 12) J Am Coll Cardiol. Acute effects of cannabis inhalation on cardiac ectopy, physical activity, sleep, and glucose