LONDON — Regular marijuana use may cause changes to the structure and function of the heart, according to a new study.
The stunning research by experts at Queens Mary University of London found that people who frequently use cannabis are at greater risk of an enlarged left ventricle. There were also early signs of impairment of heart function in users. The study’s authors believe the alarming discovery should push researchers to focus more heavily on the potential impact marijuana use could have on the heart.
“Our findings are not conclusive but the research took place against a backdrop of decriminalization and legalization of recreational cannabis use in many countries,” says lead author Dr. Mohammed Khanji, senior clinical lecturer at the university, in a statement. “We urgently need systematic research to identify the long-term implications of regular consumption of cannabis on the heart and blood vessels. This would allow health professionals and policymakers to improve advice to patients and the wider public.”
For the study, the authors examined heart scans of 3,407 adults — mostly older (average age 62) — who did not have heart disease. While the vast majority (3,255 participants) said they never or rarely use cannabis, 105 people did admit to being regular users earlier in their lives, while 47 were still using regularly.
The authors found that current cannabis users were more likely to have larger left ventricles, which is the heart’s main pumping chamber. By measuring how muscle fibers in the heart deformed during contraction, they also found that regular users also showed the onset of impaired heart function.
Individuals who previously used marijuana regularly, but had since quit, had similar heart size and function to participants who rarely or never used the drug.
Researchers say their findings controlled for age, diabetes, blood pressure, smoking, and alcohol use. But because most participants (96%) were Caucasian and only about four-dozen were regular users, the study’s results still had limitations. There could also be other health factors contributing to their conditions as well that were not controlled for in the research.
Still, Khanji warns the research points to a potentially troubling consequence of cannabis consumption at a time when laws prohibiting use of the drug continue to be lifted.
“We believe this is the first study to systematically report changes in heart structure and function associated with recreational cannabis using cardiac MRI, which is a very sensitive imaging tool and the current reference standard for assessing cardiac chambers,” he says. “The World Health Organization has warned about the potential harmful health effects of non-medical cannabis use and called for more research specifically around the cardiac impact.”
The study’s findings are published in the journal JACC Cardiovascular Imaging.