Cannabis is filled with cannabinoids, or psychoactive chemicals unique to the plant. One cannabinoid called delta-9-tetrahydrocannabinol, or THC, is what mainly causes the psychoactive effects a person feels when they smoke or ingest the plant.
Cannabinoid can increase resting heart rate and make heart beat more violently. According to a study in 2019, the literature on marijuana suggests that it affects the heart in three main ways:
Cannabis arteritis. Heavy cannabis use can inflame arteries, damage blood vessel walls, and reduce blood flow to the organs.
Cannabis-induced vasospasms. A vasospasm is when the muscular wall of an artery contracts, causing the artery to narrow and decrease the amount of blood that can go through it.
Platelet aggregation. This involves tiny blood cells called platelets clumping together and forming clots, which can block blood vessels and reduce blood flow.
Smoking marijuana might be worse for your heart than taking it in other ways, such as through edibles, says Nav Bajaj, MD, a cardiologist at the University of Alabama at Birmingham.
“When you smoke, marijuana is converted into different chemicals as well, which apart from the cannabinoids may have their own deleterious effect on the heart and the blood vessels.” However, Bajaj notes that there needs to be more studies to know for sure.
Smoking marijuana has been shown to expose you to the same toxins, irritants and carcinogens as tobacco, according to the American Lung Association. In addition, when smoking marijuana, smokers usually inhale deeper than smokers, which may lead to more tar exposure.
While Bajaj admits that smoke of all kinds can damage arteries and the heart, there’s simply not enough large scale studies to see how exactly marijuana compares to cigarettes on heart health. For reference, the Centers for Disease Control and Prevention estimate that cigarette smokers are two to four times more likely than non-smokers to develop coronary artery disease.
However, there is still a lot of conflicting research on how marijuana is related to certain cardiovascular diseases — especially heart rhythm disorders.
Though there’s still a lot we don’t know about marijuana and cardiovascular health, Bajaj notes where initial data is pointing. “I would say, you know, there is evidence of some harm, but we need to prove that conclusively,” Bajaj says.