Research was presented in November of 2016 at the American Heart Association’s Scientific Sessions that connected marijuana use and a heart muscle problem that can mimic the symptoms of a heart attack. “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.” Younger marijuana male users were twice as likely as non-users to experience this heart condition, which usually occurs in older women. They were also significantly more likely to go into cardiac arrest and need an implanted defibrillator to detect and correct the dangerously abnormal heart rhythms.

None of the people in the study who had used marijuana died after they were admitted to the hospital; so this study did not link marijuana use to sudden death. But some reports, discussed below, do report such a link. Nevertheless, one of the study’s co-authors said the link between smoking marijuana and stress cardiomyopathy in younger patients suggests the need for further investigation, especially with the growing legalization of recreational and medical marijuana in the U.S. “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.” See the article on Live Science and the press release from the American Heart Association for more information.

The above heart condition is a rare occurrence, as is sudden cardiac death with marijuana use, but the incidence rate is not zero. Thomas, Kloner and Rezkalla published an article in the January 2014 issue of The American Journal of Cardiology describing a series of marijuana-related heart problems. Thomas et al. noted that published reports describe a temporal relationship between marijuana use and developing heart problems such as: acute myocardial infarction (a heart attack), cardiomyopathy, and sudden cardiac death. Careful evaluation of the cardiovascular effects of marijuana are complicated by the fact that it is often combined with other drugs, such as alcohol or tobacco.

The mechanism underlying the association between marijuana use and myocardial infarction is currently unknown. But it seems possible cannabis has a negative effect on coronary microcirculation. One reviewed report demonstrated how marijuana use made a 34-year-old man susceptible to ventricular tachycardia. After he stopped his marijuana use, his coronary flow returned to normal. A 2010 case study by Karabulut and Cakmak in Kardiologia Polska documented the existence of slow coronary flow in an individual who consumed marijuana regularly over a long period of time.

In “Triggering Myocardial Infarction by Marijuana,” Mittleman et al. interviewed 3,882 individuals an average of four days after the onset of myocardial infarction. The risk of myocardial infarction was 4.8 times higher in the sixty minutes after marijuana use. The risk rapidly decreased afterwards. They were less likely to have a history of angina or hypertension. Showing the presence of the above noted complicating factors, they also tended to be current cigarette smokers and obese.

Thomas, Kloner and Rezkalla noted where most case reports described relatively young patients in their 20s or 30s with normal coronary arteries or minimal atherosclerosis. This suggested that marijuana does not lead to or accelerate atherosclerotic damage in healthy adults and might explain the rarity of reports of marijuana-associated myocardial infarction despite the widespread use of the drug.

Marijuana use may also precipitate the development of myocardial infarction in patients with coronary artery disease. After myocardial infarction, mortality is signiifcantly higher in marijuana users than in the general population. In a study of 1,913 adults after hospitalization for myocardial infarction, Mukamal et al found a 4.2-fold increased risk for mortality in marijuana users who reported consuming the drug more than once per week before the onset of the infarction compared with nonusers.

Reports of marijuana use and sudden death are rarer than those of myocardial infarction, but nevertheless still evident. Most patients were abusing other drugs along with marijuana, precluding an accurate conclusion about the role played by marijuana in the cause of death. Yet there was a case report in the December 2001 issues of Forensic Science International by Bachs and Morland, “Acute cardiovascular fatalities following cannabis use,” of six possible cases of acute cardiovascular death in young adults, who had very recent cannabis use. This was confirmed by the presence of THC in post mortem blood samples; no other drugs were present. The article abstract noted where similar cases have been reported, but the toxicology reports were absent or limited to just urine samples.

The authors also speculated on the underlying mechanisms to these adverse effects. They acknowledged that currently relatively little is known about the underlying mechanisms at this point in time. Yet they noted several features of marijuana use that may explain the potential for an adverse effect on patients with known coronary artery disease. For example, marijuana is known to increase heart rate.

Supporting these findings, the American College of Cardiology described the following effects of marijuana on the cardiovascular system. In “Marijuana and Coronary Heart Disease,” the cardiovascular effects of marijuana included: elevated systolic and diastolic blood pressure, tachycardia,elevated sympathetic stimulation, decreased time to angina, increased risk of myocardial infarction for one hour after marijuana use.

A 2006 study based on data from The Coronary Artery Risk Development in Young Adults (CARDIA) study showed that marijuana use was associated with increased appetite, high caloric diet, and acute increase in blood pressure. “Although marijuana was not independently associated with cardiovascular risk factors, it was associated with other unhealthy behaviors … which all have long-term detrimental effects on health.”

There seems to be a consensus with the following remarks by Thomas, Kloner and Rezkalla to cardiologists and their patients alike:

In conclusion, the potential for increased use of marijuana in the changing legal landscape suggests the need for the community to intensify research regarding the safety of marijuana use and for cardiologists to maintain an awareness of the potential for adverse effects.