Heart attacks are significantly more prevalent in US adults under 45 who use cannabis than those who don't, according to researchers, who dispute the idea that cannabis is safe. Their study, published Tuesday in the Canadian Medical Association Journal, looks at the health data of more than 33,000 US adults ages 18 to 44 taken from surveys conducted by the CDC from 2017 and 2018, per CNN. Some 17.5% reported using cannabis in some form—whether by smoking, vaping, or consuming it as an edible—within the past 30 days. Of those, 1.3% later had a heart attack. That's almost twice the rate of nonusers at 0.8%.
A history of heart attack was also associated with smoking as the primary method of consumption, and with frequent cannabis use (more than four times per month). "The more people use, the higher the risk," study author Dr. Karim Ladha, a clinician scientist at the University of Toronto, tells Global News. Less frequent use meant an "elevated, albeit nonsignificant" risk relative to nonusers. Researchers found cannabis users were more likely to be male, unmarried, smokers of cigarettes and e-cigarettes, and heavy consumers of alcohol. In other words, their habits carried additional heart attack risks. But researchers say the results were consistent after adjusting for those factors.
While the link between cannabis use and heart attacks isn't fully understood, past studies suggest cannabis use increases heart rate while decreasing the amount of oxygen delivered to the heart. "We know there are lots of people using cannabis and not everybody is dropping dead from a heart attack," but "that mismatch between supply and demand of oxygen, that's what fundamentally leads to any kind of [heart attack]," Ladha tells the Canadian Press. "We know that cannabis has the potential to do this, but we didn't really appreciate that even younger adults could be at risk." (Another study shows a link between increased cases of schizophrenia and cannabis use disorder.)