New research reveals a stark warning for cannabis users: marijuana significantly increases the risk of dangerous heart rhythm problems that can prove fatal.
A large-scale study published in August 2025 by researchers from the University of California, Georgetown University, and multiple other medical institutions found that cannabis use substantially raises the likelihood of developing serious cardiac arrhythmias. The findings show cannabis users face more than triple the risk of ventricular tachycardia and ventricular fibrillation compared to non-users.
Understanding the Risk
The retrospective study analysed electronic health records from 68 U.S. healthcare organizations, examining over 210,000 cannabis users matched with a similar number of control subjects. Researchers found 97 cases of ventricular tachycardia or fibrillation among cannabis users versus only 35 cases in the control group, representing a hazard ratio of 3.078.
Ventricular arrhythmias represent the most severe type of irregular heartbeat. These conditions occur when the heart’s lower chambers beat too quickly or chaotically, potentially preventing the heart from pumping blood effectively. Without immediate treatment, ventricular fibrillation can cause sudden cardiac death within minutes.
Beyond Ventricular Arrhythmias
The study documented elevated risks across multiple types of heart rhythm disorders. Cannabis users showed 1,895 cases of atrial fibrillation or flutter compared to 1,332 in the control group, with a 55% increased risk. Paroxysmal tachycardia occurred in 1,065 cannabis users versus 672 controls, representing a 79% increased risk, while premature beats affected 1,135 cannabis users compared to 745 controls, a 74% increase.
Atrial fibrillation emerged as the most common arrhythmia among cannabis users, though less immediately dangerous than ventricular arrhythmias. Atrial fibrillation still carries serious consequences, including increased stroke risk and heart failure.
Why Cannabis Affects Heart Rhythm
Multiple mechanisms may explain how cannabis triggers arrhythmias, including THC’s ability to block cardiac ion channels and prolong the QT interval. THC also enhances sympathetic nervous system activity through CB1 receptor activation, increasing heart rate and susceptibility to irregular rhythms.
Cannabis can cause coronary vasospasm and endothelial dysfunction, creating conditions that promote arrhythmias. Chronic use may lead to cardiac inflammation and fibrosis, causing atrial remodelling directly linked to atrial fibrillation development.
Research suggests the highest risk period occurs within one to two hours after cannabis use, indicating acute exposure poses immediate danger.
A Growing Public Health Concern
As cannabis legalization expands, hospitalization rates for cannabis-related arrhythmias have increased 31% over the past decade. The rise in arrhythmia-related hospitalizations appears particularly pronounced among teenage cannabis users.
Cannabis-induced arrhythmias disproportionately affect young, otherwise healthy individuals without structural heart disease, challenging assumptions that heart rhythm problems primarily afflict older adults with existing cardiovascular conditions.
The study used propensity score matching to ensure fair comparison between groups, accounting for age, sex, cardiovascular risk factors, and medication use. This rigorous methodology strengthens confidence in the findings.
What This Means for Users
Healthcare providers should counsel patients about cardiovascular risks associated with cannabis, particularly those with pre-existing heart conditions. The cardiovascular effects of marijuana deserve serious consideration as legal access continues expanding nationwide.
For individuals using or considering cannabis, these findings provide important context. Heart arrhythmias represent serious medical emergencies requiring immediate attention. Anyone experiencing symptoms like rapid heartbeat, chest pain, dizziness, or fainting should seek medical care promptly.
The research adds to mounting evidence documenting adverse cardiovascular effects of cannabis use. As the scientific community continues investigating these risks, current data already provide clear cause for concern about marijuana’s impact on heart health.
Source (WRD News)
