They say absence makes the heart grow fonder. In the case of marijuana, decreased usage may not make the heart fonder, but it could prove to keep it healthier as new evidence points to increased risk of stroke and heart failure for marijuana users. The findings from this new study are set to be presented at the upcoming American College of Cardiology's (ACC) 66th Annual Scientific Session in a presentation entitled “Cannabis Use Predicts Risks of Heart Failure and Cerebrovascular Accidents: Results from the National Inpatient Sample.”
Coming at a time when marijuana is on track to become legal for medical or recreational use in more than half of U.S. states, this study sheds new light on how the drug affects cardiovascular health. While previous marijuana research has focused mostly on pulmonary and psychiatric complications, the new study is one of only a handful to investigate cardiovascular outcomes. For instance, a recent study described a phenomenon of increased incidence of stress-induced cardiomyopathy—typically seen in older females—among young, male marijuana users.
“Like all other drugs, whether they're prescribed or not prescribed, we want to know the effects and side effects of this drug,” remarked lead study investigator Aditi Kalla, M.D., a cardiology fellow at the Einstein Medical Center in Philadelphia. “It's important for physicians to know these effects so we can better educate patients, such as those who are inquiring about the safety of cannabis or even asking for a prescription for cannabis.”
For the study, Dr. Kalla and her colleagues gathered data from the Nationwide Inpatient Sample, which includes the health records of patients admitted to more than 1000 hospitals comprising about 20% of U.S. medical centers. Researchers extracted records from young and middle-aged patients—ages 18 to 55 years—who were discharged from hospitals in 2009 and 2010 when marijuana use was illegal in most states.
Marijuana use was diagnosed in about 1.5% (316,000) of more than 20 million health records included in the analysis. Comparing cardiovascular disease rates in these patients to disease rates in patients not reporting marijuana use, researchers found marijuana use was associated with a significantly increased risk for stroke, heart failure, coronary artery disease, and sudden cardiac death.
Additionally, marijuana use was also linked with a variety of factors known to increase cardiovascular risks, such as obesity, high blood pressure, smoking, and alcohol use. After researchers had adjusted the analysis to account for these factors, marijuana use was independently associated with a 26% increase in the risk of stroke and a 10% increase in the risk of developing heart failure.
“Even when we corrected for known risk factors, we still found a higher rate of both stroke and heart failure in these patients, so that leads us to believe that there is something else going on besides just obesity or diet-related cardiovascular side effects,” Dr. Kalla remarked. “More research will be needed to understand the pathophysiology behind this effect.”
Dr. Kalla and her colleagues are interested in uncovering the underlying molecular mechanisms that lie at the center of their observations. Since previous studies have shown that heart muscle cells have cannabis receptors relevant to contractility, or squeezing ability, the investigators hypothesize that those receptors might be one pathway through which marijuana use could affect the cardiovascular system. The researchers are hopeful that if they are correct, compounds could be developed to counteract that mechanism and reduce cardiovascular risk.
While the researchers found their results interesting, they urged caution against overinterpretation as the study was based on hospital discharge records and the findings may not be reflective of the general population. Moreover, the study was also limited by the researchers' inability to account for quantity or frequency of marijuana use, the purpose of use (recreational or medical), or delivery mechanism (smoking or ingestion).
Dr. Kalla suggested that the growing trend toward legalization of marijuana could mean that patients and doctors will become more comfortable speaking openly about marijuana use, which could allow for better data collection and further insights into the drug's effects and side effects.