In the United States, marijuana is the most commonly used illegal drug. 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.

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Smoking marijuana may lead to heart problems.

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.

What is stress cardiomyopathy?

Stress cardiomyopathy is popularly referred to as "broken heart syndrome" because it can be caused by extreme emotional stressors, such as grief, fear, surprise, and anger.

The condition can also be caused by physical stressors, such as stroke, seizure, breathing difficulties, or heavy bleeding.

According to the Johns Hopkins Heart and Vascular Institute, the symptoms of stress cardiomyopathy are very similar to those of a heart attack, and they include chest pain, shortness of breath, dizziness, and palpitations. This is due to the heart's temporary inability to pump blood.

However, unlike a heart attack, stress cardiomyopathy does not kill any heart cells; instead, it temporarily stuns them using adrenaline and other hormones. As a result, recovery from broken heart syndrome is quick and leaves no permanent damage.

Dr. Amitoj Singh, chief cardiology fellow at St. Luke's University Health Network in Bethlehem, PA, led a study where he examined the link between stress cardiomyopathy and marijuana use.

The results of the research were presented at the American Heart Association's Scientific Sessions 2016 in New Orleans, LA.

Marijuana use may double the risk of stress cardiomyopathy

Researchers looked at 33,343 people who were admitted to the hospital with stress cardiomyopathy between 2003-2011. The data was taken from the Nationwide Inpatient Sample.

Of these patients, 210 - less than 1 percent - were also marijuana users. Active marijuana use was established either from the information provided by the patient, or by testing for markers in the patient's urine.

Marijuana users were more than twice as likely to develop stress cardiomyopathy than nonusers.

They were also more likely to be younger, male, and have fewer risk factors for cardiovascular disease, such as diabetes, high blood pressure, or high cholesterol.

However, even after adjusting for the already low cardiovascular risk factors, marijuana users were more likely to go into cardiac arrest during stress cardiomyopathy than nonusers.

Marijuana users had a 2.4 percent risk of going into cardiac arrest, compared with the 0.8 percent risk in nonusers.

Marijuana users were also more likely to require an implanted defibrillator to stabilize dangerously abnormal heart rhythms, with a 2.4 percent likelihood, compared with 0.6 percent in nonusers.

Researchers also adjusted for other risk factors that are normally associated with stress cardiomyopathy, as well as factors cannabis users were far more likely to have.

These included a higher likelihood of depression, (32.9 percent compared with 14.5 percent in nonusers), tobacco use (73.3 percent compared with 28.6 percent in nonusers), psychosis (11.9 percent versus 3.8 percent in nonusers), and anxiety disorder (28.4 percent likelihood compared with 16.2 percent in nonusers).

Further research needed to confirm causality

"This development of stress cardiomyopathy in younger patients who used marijuana suggests a possible link that needs to be further investigated," says Dr. Sahil Agrawal, co-author of the study and 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."

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.

Read about a study that sheds light on the marijuana receptor CB1.