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Researchers at Brigham and Women's Hospital estimate that more than 2 million Americans with serious heart disease use marijuana — and they say that could be a cause for concern.
Brigham cardiologist Muthiah Vaduganathan says the research team broadly reviewed what's known about how marijuana acts on the body, including on heart cells, and its possible links to strokes, heart attacks and other health issues.
"We conclude that based on the available, limited evidence, marijuana should be limited or not used in our highest-risk patients with known cardiovascular disease," he says. Those include patients who've recently been treated for a heart attack, abnormal heart rhythm or failing heart muscle.
Vaduganathan says more research is badly needed, and meanwhile, doctors should be sure to ask cardiac patients whether they use marijuana, so it can be factored into their treatment. For example, cannabis can affect the metabolism of drugs like statins, which are often prescribed for high cholesterol, and blood-thinners.
For their review in the Journal of the American College of Cardiology, the research team mined national survey data to estimate how many heart-disease patients use cannabis as legalization increases its popularity.
The study drew its conclusions at a population level, Vaduganathan says, but at the level of individual patients, "maybe those conversations need to be more nuanced." Patients use marijuana for various reasons, he notes, and may need it for important medical conditions such as end-of-life pain relief.
Smoking marijuana raises particular health concerns, he says, because the toxic combustion products of smoked marijuana are very similar to those of cigarettes.
"While cigarette smoking is declining in the United States, marijuana use — for the first time — now outpaces the use of cigarettes in the United States," he says. "And so as clinicians, we need to broadly tackle this and understand the global cardiovascular effects."
Even if marijuana is not smoked and so poses little risk to lungs, there is still concern that it could cause cardiovascular harm, he says. But almost no rigorous research has been done on those effects, he adds, because it's classified as a Schedule 1 drug.
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