A 14-day randomized crossover trial in 108 regular cannabis users found about 9% fewer premature heartbeats on days they smoked or vaped cannabis than on abstinence days.
The reduction came from fewer premature atrial contractions—beats from the heart’s upper chambers that can predict atrial fibrillation—while lower-chamber PVCs showed no significant change.
Continuous monitors also found no differences in sleep, step counts or blood glucose, though researchers said heart-rate patterns shifted as expected during cannabis use.
Gregory Marcus said the findings should not be taken as proof cannabis benefits cardiovascular health, and they are not enough to change clinical guidance or behavior.
The UCSF team said the trial, among the first randomized real-world studies of inhaled cannabis, challenges observational assumptions but follows broader evidence—including a 2024 study of 430,000 adults—linking frequent use to higher heart attack and stroke risk.