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By MK Manoylov, Insider
Smoking cigarettes is known to be one of the biggest risk factors for heart disease. And with more states legalizing marijuana and more people smoking cannabis, it's worth considering how it compares to tobacco.
While research is limited on how marijuana affects the body, here's what we know so far about what it does to the heart.
How marijuana affects the heart
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.Cannabinoids raise resting heart rate and make the heart pump harder. According to a 2019 study, the literature available on cannabis suggests it can affect the heart in three major 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 is likely worse for your heart than edibles
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.
According to the American Lung Association, smoking marijuana has been shown to expose you to the same toxins, irritants, and carcinogens as smoking tobacco. Moreover, when smoking marijuana, users often inhale more deeply than cigarette smokers, and that can 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.
Marijuana and heart disease
According to a 2019 systematic review, marijuana may lead to a higher risk of heart disease. Out of the 33 studies included, 28 found that marijuana use can increase the risk of chronic cardiovascular disease and acute coronary syndrome, which involves a sudden rupture of plaque inside the coronary artery and may lead to a heart attack.In addition, Bajaj and his team recently published a study in the Journal of the American College of Cardiology investigating how marijuana affects those with cardiovascular disease. An estimated 2 million people with cardiovascular disease consume marijuana, though Bajaj notes it's likely that number is under reported.
In people with atherosclerotic cardiovascular diseases — or those involving a buildup of plaque in the arteries — cannabis can cause harm by increasing blood pressure and heart rate and activating the sympathetic nervous system, which controls the fight or flight stress response.
According to Bajaj's study, this response can increase how much oxygen the heart needs. When combined with factors of heart disease, such as a buildup of plaque in the cardiac arteries, this can lead to dangerous heart conditions. For example, reduced oxygen to the heart combined with a blocked heart artery can lead to a heart attack.
Further research on marijuana and the heart is needed
However, there is still a lot of conflicting research on how marijuana is related to certain cardiovascular diseases — especially heart rhythm disorders.For example, some studies have found that cannabis use is associated with a higher risk of arrhythmias like ventricular tachycardia, ventricular fibrillation, and atrial fibrillation. But others have suggested that marijuana has no effect on ventricular tachycardia or ventricular fibrillation, and that it may even reduce the risk of atrial fibrillation.
In addition, some experts say that marijuana use does not pose a significant threat to people at little risk for heart disease. But another study found that young people who smoke marijuana for more than 10 days a month are 2.5 times more likely to have a stroke than non-users — even if they don't use tobacco products.
Many of these studies have yet to establish any causal link between marijuana use and cardiovascular disease, and the presence of an association may not indicate that marijuana is responsible for causing a stroke or arrhythmia.
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.
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