Cannabis was under discussion at the American Heart Association’s Scientific Sessions 2020 (held November 13–17), with some potential red flags being raised for those with pre-existing heart disease.
Two studies presented at the sessions touched on the effects of marijuana on heart health, with both having unexpected twists.
In the first, which looked at data from 113,477 patients in Michigan, marijuana users who underwent an angioplasty to clear blocked arteries were more likely to experience stroke and bleeding after the procedure than those who weren’t users.
The second study looked at patients who had an artery clearing procedure after a heart attack, and found that those in this group who said they'd used marijuana were more likely than those who had not to have a subsequent heart attack.
The twists in the tails of these two studies were as follows: in the first study, despite the higher stroke and bleeding risk, those who smoked cannabis were less likely to have sudden kidney failure—something the researchers were at a loss to explain.
In the second study, even though cannabis smokers were more likely to have a second heart attack (7.2 percent of this group, versus 4.5 percent of non-smokers), they actually had lower classic heart attack risk factors including hypertension, diabetes and high cholesterol.
“Marijuana is becoming more accessible, and patients should be aware of the increased risk after angioplasty,” the University of Michigan’s Dr. Sang Gune Yoo, lead researcher of the first study, told NBC News.
Commenting on the findings of both studies, Dr. Peter Grinspoon—an instructor at Harvard medical school, cannabis expert, and board member for Doctors for Cannabis Regulation added: “Looking at the totality…they seem to contain some contradictory findings. [But] by their measures, they’ve actually shown that cannabis decreases kidney damage, which should be a huge headline in itself.”
Doctors do not know if it is the cannabis, specific chemicals in the cannabis, or the smoke that may be leading to cardiac issues, although other studies have shown THC in cannabis does raise heart rate and blood pressure. More research is certainly needed but this is hampered by the plant’s federals designation as a Schedule I narcotic.