While the effects of marijuana on the cardiovascular system remain largely unknown, a new study suggests that marijuana use may double the risk of stress cardiomyopathy, a condition where the heart muscles are quickly and severely weakened.
According to the Centers for Disease Control and Prevention (CDC), in 2013, 19.8 million Americans aged 12 years or older reported having used marijuana in the preceding month. In 2014, that number had increased at a rate of approximately 7,000 new users every day.
More and more people perceive the use of marijuana as completely harmless. Between 2002-2014, the CDC report that the perceived risk of marijuana decreased, while the number of people who perceived marijuana as risk-free increased.
But a new study suggests there may be a link between the use of marijuana and an uncommon heart muscle malfunction.
The researchers found that marijuana users were almost twice as likely to develop stress cardiomyopathy compared to non-users, even after taking other cardiovascular risk factors into consideration. Active marijuana use was identified either by information provided by the patient in their medical history, or by a marker in the patient’s urine.
Stress cardiomyopathy is a sudden, usually temporary, weakening of the heart muscle that reduces the heart’s ability to pump, leading to chest pain, shortness of breath, dizziness and sometimes fainting.
“The effects of marijuana, especially on the cardiovascular system, are not well known yet. With its increasing availability and legalization in some states, people need to know that marijuana may be harmful to the heart and blood vessels in some people,” said Amitoj Singh, M.D. study co-author and chief cardiology fellow at St. Luke’s University Health Network in Bethlehem, Pennsylvania.
Compared with non-users, researchers found that marijuana users were more likely to be younger, male with fewer cardiovascular risk factors, including less high blood pressure, diabetes and high cholesterol.
However, despite being younger and with fewer cardiovascular risk factors than non-users, during stress cardiomyopathy the marijuana users were significantly more likely to go into cardiac arrest (2.4 percent vs. 0.8 percent) and to require an implanted defibrillator to detect and correct dangerously abnormal heart rhythms (2.4 percent vs. 0.6 percent).
“This development of stress cardiomyopathy in younger patients who used marijuana suggests a possible link that needs to be further investigated,” said Sahil Agrawal, M.D., co-author of the paper and also a chief cardiology fellow at St. Luke’s.
As this is an observational study, however, it cannot establish causality. Therefore we cannot say whether marijuana directly causes stress cardiomyopathy. But if users experience heart problems, the authors warn, they should see a doctor.
"If you are using marijuana and develop symptoms such as chest pain and shortness of breath, you should be evaluated by a healthcare provider to make sure you aren't having stress cardiomyopathy or another heart problem." Said Dr. Amitoj Singh.
Researchers did not have access to data from all of the nation's states, but instead focused on regional reports. As a result, researchers could not establish whether marijuana-related stress cardiomyopathy has a higher incidence rate in those states where recreational use is legal. These may be useful directions for future research.
As Dr. Singh says: "The effects of marijuana, especially on the cardiovascular system, are not well known yet. With its increasing availability and legalization in some states, people need to know that marijuana may be harmful to the heart and blood vessels in some people."
Finally, scientists were unable to analyze how often participants used marijuana, or how much time had passed between marijuana intake and the occurrence of stress cardiomyopathy.