Recognizing the possible adverse health effects of smoking pot to get high, the researchers examined the link between marijuana use and heart health.
The researchers, from St. Luke's University Hospital Network, focused on patients with stress cardiomyopathy, a sudden temporary weakening of the heart muscle that prevents it from pumping. Patients with the condition, which has been said to mimic a heart attack, can experience acute chest pain, shortness of breath and dizziness.
The muscle weakness is most often caused by acute stress or grief, such as a breakup or the death of a loved one. However, according to Dr. Amitoj Singh, the lead investigator of the study, at least two cases of stress cardiomyopathy in medical literature have been related to marijuana use.
"There have been many reports of heart attacks, strokes and the two cases of (stress cardiomyopathy) that have been linked to marijuana," Singh said.
Greater availability of marijuana, particularly for recreational use, has heightened concern in the medical community about cardiac risks, sparking Singh's interest.
Using Nationwide Inpatient Sample data from 2003 to 2011, the researchers tracked hospital admissions and outcomes of 33,343 patients with stress cardiomyopathy. The data were taken from across the country and represented both men and women of varied ages. Two groups were formed from the data: one group of marijuana users (which had 210 patients, or 1% of the total study pool) and a group of patients who did not use the drug.
Each group was strikingly different in terms of demographics, medical histories and outcomes. The marijuana users tended to be younger and more often male, a finding that was surprising to Singh, because stress cardiomyopathy most often occurs in older women, he said.
Marijuana users also had fewer risk factors that typically cause stress cardiomyopathy, such as acute stress, hypertension, diabetes, migraines and hyperthyroidism. The non-marijuana-using group had much higher rates of these conditions.
"Even though these young people had less cardiac risk factors, they still had high cardiac risk," Singh said.
Marijuana users also suffered more severe cardiac problems. "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% vs. 0.8%) and to require an implanted defibrillator to detect and correct dangerously abnormal heart rhythms (2.4% vs. 0.6%)," the American Heart Association said of the study in a news release.
Investigating further, the researchers created a model that excluded all of the known causes of stress cardiomyopathy to see whether marijuana use alone could trigger the condition. They found a statistically significant relationship between the drug and stress cardiomyopathy, Singh said.
"Someone who uses marijuana is almost two times more likely to develop stress cardiomyopathy," he explained.
However, the report also found that marijuana users were more likely to use tobacco and illicit substances, as well as suffer from depression, than non-marijuana users.
Dr. Ann Bolger, a professor of clinical medicine at the University of California, San Francisco School of Medicine and a spokeswoman for the American Heart Association, said these factors can contribute to stress cardiomyopathy. "It's hard to know exactly that you can account for all of these other contributors" when determining causation of the condition, she said.
Should you avoid marijuana?
Bolger agrees with the overall concern raised by the new study. "It does give me some very appropriate worry that exposure to (marijuana) may not be as benign as some people seem to think."
She added that "If this is in some way predictive of poor outcomes or indicative that we need to have concern about the cardiovascular health and outcomes of patients using marijuana, I think it's a very good thing to start to think about."
Singh acknowledges that marijuana has several benefits in medicine, particularly with treatments such as chemotherapy. "We don't want to underestimate the benefits of medical marijuana," he confirmed.
Still, Singh wants to draw attention to the potential harms of recreational use. The lack of regulation makes it difficult for users to know the amount of THC, the psychosis-inducing chemical in marijuana, contained in a dose, which can be dangerous. Singh is still not certain whether THC is principally responsible for users' cardiac problems; that is a topic that needs to be further studied, he said.
As a whole, more research needs to be done regarding the effects of marijuana on heart health, Singh emphasized.
"This is a retrospective study, so we cannot determine causation" between marijuana and weakening heart muscles, he concluded. "Further research is needed to evaluate this study, especially considering the current increase of recreational marijuana in our country."