To use marihuana every day can increase a person’s risk of coronary artery disease, or CAD, by one-third compared with those who never use it, a new study found.
“A growing body of evidence suggests that the cannabis it is not entirely harmless and can actually cause cardiovascular disease,” said the study’s lead author, Ishan Paranjpe, a resident physician at Stanford University, in the United States. The study – which has not yet been published – will be presented on Sunday (26) at the annual meeting of the American College of Cardiology.
“Thus, the decision to use cannabis must be carefully weighed against the potential for serious heart disease,” said Paranjpe.
Coronary artery disease is caused by plaque buildup on the walls of the arteries that supply the heart with blood. Also called atherosclerosis, CAD is the most common type of heart disease, according to the US Centers for Disease Control and Prevention (CDC).
Signs of the condition include having angina or chest pain, feeling weak, dizzy or nauseous, or feeling short of breath. However, for “some people, the first sign of CAD is a heart attack,” says the CDC on its website.
Using once a month or less
The study drew data from people who participated in the All of Us Research Program. Administered by the National Institutes of Health, the program is designed to collect health information over time from 1 million or more people in the United States.
Upon enrolling in the study, participants completed a survey about their cannabis use. The research team used this information to sort respondents into five categories: daily users (4,736 people), weekly users (2,720), monthly users (2,075), users who used it once or twice in three months (8,749), and users who never used it (39,678 people). The researchers then compared these categories with the participants’ medical records a few years later.
They found that daily cannabis users were 34% more likely to be diagnosed with coronary artery disease than those who never used the drug. People who used marijuana only once a month or less had no significant risk, the study found.
The results held true even after the researchers accounted for other potential causes of coronary heart disease, such as age, gender and major cardiovascular risk factors – high blood pressure, high cholesterol, type 2 diabetes, obesity, smoking and alcohol use.
The study used Mendelian randomization (MR) to determine risk, which other studies on the subject have not done, Paranjpe said in an email. The MR method measures genetic variations known to be related to a modifiable risk factor to determine the causal influence of the risk factor.
“Although other work has also linked cannabis with CAD, there are several potential confounders that could explain this relationship. Our MR analysis suggests that this relationship may be directly causal,” said Paranjpe.
Marijuana and the heart
Why does marijuana seem to damage the heart and blood vessels? First, it increases heart rate and blood pressure immediately after each use, according to the CDC.
“Marijuana smoke also provides many of the same substances that researchers have found in tobacco smoke – these substances are harmful to the lungs and cardiovascular system,” says the agency.
Smoking or vaping any substance, including cannabis, should be avoided due to the risk of damage to the heart, lungs and blood vessels, the American Heart Association (AHA) warned in 2020.
The AHA guidance released then pointed to studies that found that heart rhythm abnormalities, such as tachycardia and atrial fibrillation, could occur within an hour of smoking marijuana containing delta-9-tetrahydrocannabinol, or THC. (THC is the part of the marijuana plant that gives you a high.)
Other research has shown that smoking marijuana triggers heart attacks and leads to a higher risk of strokes and heart failure in people with underlying heart conditions.
Notably, the new study was unable to determine whether different types of cannabis use — such as consuming edibles versus smoking marijuana, for example – made a difference in a person’s risk of developing CAD. However, because THC reaches the brain more quickly when smoked, the researchers argue that future research should investigate various methods of use and their impact on the heart.
Source: CNN Brasil

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