News

Study finds fewer premature heartbeats after cannabis use

Published on August 19, 2026 by oz. staff

Photo: Adobe Stock/the oz.

Cannabis users experienced fewer premature heartbeats on days they inhaled cannabis than on days they abstained, according to a new study that surprised even the researchers conducting it.

The randomized study, published Aug. 12 in the Journal of the American College of Cardiology, found habitual cannabis users experienced about 9% fewer premature heartbeats on days they smoked or vaped cannabis.

The findings run counter to the researchers’ original hypothesis that cannabis use would increase abnormal heartbeats.

“We were surprised by the results because they contradicted our original hypothesis,” study researcher Dr. Gregory Marcus, a professor in the University of California, San Francisco’s Division of Cardiology, said in a UCSF news release.

“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.”

The study followed 108 adults who regularly smoked or vaped cannabis but had no history of clinically diagnosed cardiac arrhythmias.

Over a 14-day period, participants were randomly assigned each day to either use cannabis or abstain. Participants acted as their own controls, allowing researchers to compare what happened to the same person’s body on cannabis-use and abstinence days.

They wore continuous electrocardiogram monitors along with devices tracking physical activity, sleep and glucose levels.

Fewer premature atrial contractions

Researchers found cannabis inhalation was associated with a statistically significant reduction in cardiac ectopy, the medical term for extra or premature heartbeats.

The reduction was primarily driven by fewer premature atrial contractions, or PACs, which originate in the heart’s upper chambers.

PACs are common and aren’t necessarily dangerous on their own, but their frequency can be an important predictor of atrial fibrillation.

Researchers did not find a significant change in premature ventricular contractions, or PVCs, which originate in the heart’s lower chambers.

The study also found no significant differences in participants’ daily step counts, sleep duration or glucose levels between cannabis and abstinence days.

The research is notable because much of the previous evidence examining cannabis and cardiovascular health has come from observational studies relying on medical records or self-reported cannabis use.

In this case, researchers continuously monitored participants as they went about their everyday lives while randomly assigning cannabis-use and abstinence days.

Researchers urge caution

Despite the unexpected findings, researchers stressed that the study does not show cannabis is good for the heart.

“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,” Marcus said.

“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 distinction is important.

The participants were already habitual cannabis users, the study lasted only two weeks and researchers were examining the immediate effects of inhaled cannabis rather than the potential consequences of years of use.

The study also doesn’t establish that cannabis should be used to prevent or treat abnormal heart rhythms.

Instead, Marcus said understanding why researchers observed fewer premature atrial contractions could eventually provide clues for developing new ways of preventing or treating abnormal heart rhythms.

The findings add another wrinkle to an increasingly complicated body of research examining cannabis and cardiovascular health: sometimes, when cannabis is studied under controlled conditions, the results aren’t what researchers expected.