When someone's heart rate becomes irregular, it can increase the amount of oxygen the heart needs, Ladha explained. At the same time, cannabis can also limit the amount of oxygen delivered to the heart, he added.
"What you end up having is this mismatch of oxygen supply and demand which fundamentally leads to heart attacks," Ladha said.
Modern Cannabis Is Extremely Potent
Cannabis sold on the market today is also much more potent than cannabis sold in the past 50 years, said Robert Page, chair of the American Heart Association scientific statement on cannabis. Page was not involved in the study.
"This isn't what your granddaddy used to smoke at Woodstock; this is highly potent," he said.
Many people are not aware that cannabis can have negative interactions with other medications, Page added.
Like most other medications, cannabis is metabolized through the liver, which means it has the potential to interact with many cardiovascular medications like blood thinners, he said.
Research from the AHA also details potential benefits of using cannabis for pain relief and other medical purposes, but the negative consequences shouldn't be ignored, said study co-author Dr. David Mazer, anesthesiologist at St. Michael's Hospital and professor in the departments of anesthesia and physiology at the University of Toronto in Canada.
Both cannabis users and their health care providers should "balance the risks and benefits for cannabis in their own specific context," Mazer said.
The AHA does not recommend smoking or vaping cannabis in any quantity, Page said. Its researchers noted a potential association with stroke, and vaping has been associated with lung damage, he said.
In the future, Ladha said he wants to study cannabis users in real-time instead of looking at survey results retroactively.
It's difficult to run that type of study because cannabis is not legal in every state or at the US federal level, he noted.