Marijuana has been widely touted for its health benefits, but a new study by researchers at Einstein Medical Center in Philadelphia has found that the use of marijuana could increase adults risk of stroke and heart failure.

Researchers studied 20 million health records from patients 18 to 55 years old who were discharged from one of more than a thousand hospitals across the United States in 2009 and 2010.

1.5 percent of these patients said they’d used marijuana, and the researchers associated this use with a higher risk for stroke, coronary artery disease, heart failure, and sudden cardiac death. Pot use was also tied to common heart disease risk factors such as obesity, high blood pressure, smoking, and drinking.

Lead researcher Dr. Aditi Kalla explained, “Even when we corrected for known risk factors, we still found a higher rate of both stroke and heart failure in these patients…that leads us to believe that there is something else going on besides just obesity or diet-related cardiovascular side effects. It’s important for physicians to know these effects so we can better educate patients.”

But like any new finding, not everyone believes these conclusions are as bad as they sound. The deputy director of the marijuana advocacy group NORML, Paul Armentaro, says the increase in heart risk is, “a relatively nominal one,” and that the study “is inconsistent with the findings of several other longitudinal studies finding that those who consume cannabis, but not tobacco, suffer no greater likelihood of adverse events compared to those with no history of use.”

However, Armentaro does concede that those with pre-existing conditions that may be affected by marijuana use should use caution. “As with any medication, patients should consult thoroughly with their physician before deciding whether the medical use of cannabis is safe and appropriate,”

Dr. Andrew Rogove, who directs stroke care at Southside Hospital in Bay Shore, N.Y. says that this new study “suggests that marijuana may not be as safe as proponents for its legalization claim…further studies need to be performed to elucidate how marijuana use can increase risk for stroke and heart failure and if any particular way that it is used confers a higher risk.”

These findings should be considered preliminary until published in a peer-reviewed journal.