(CNN) — Daily marijuana use can increase the risk of coronary heart disease by a third compared to never users, according to a new study.
“There is increasing evidence that cannabis is not entirely free of harmful effects and can cause cardiovascular disease,” says Dr. Ishan Paranjpe, the study’s lead author and resident physician at Stanford University. The study, which has not yet been published, will be presented this Sunday at the annual meeting of the American College of Cardiology.
“Therefore, the decision to use cannabis must be carefully weighed against the possibility of serious heart disease,” Paranjpe said.
Coronary heart disease is caused by the buildup of plaque on the walls of the arteries that supply blood to the heart. Also called atherosclerosis, it’s the most common type of heart disease, according to the US Centers for Disease Control and Prevention (CDC).
Signs of this disease are angina, feeling weak, dizzy or upset stomach, or shortness of breath. However, for “some people, the first sign of coronary heart disease is a heart attack,” the CDC states on its website.
Consume 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 (NIH), the program is designed to collect health information over time from one million or more people in the United States.
Upon enrolling in the study, participants filled out a survey about their cannabis use. The research team used that information to classify respondents into five categories: daily users (4,736 people), weekly users (2,720), monthly users (2,075), those who used once or twice in three months (8,749), and those who never consumed (39,678 people). The researchers then compared those categories to the participants’ medical records a few years later.
They found that daily cannabis users were 34% more likely to be diagnosed with coronary heart disease than those who had never used the drug.
People who only used marijuana once a month or less were not at significant risk, according to the study.
The results held even after the investigators accounted for other potential causes of CHD, including age, gender, and major cardiovascular risk factors (hypertension, hypercholesterolemia, type 2 diabetes, obesity, smoking, and alcohol use). ).
The study used Mendelian randomization (MR) sampling to determine risk, something that other studies on the subject have not done, Paranjpe explains in an email. The RM method measures genetic variations known to be associated with a modifiable risk factor to determine the causal influence of the risk factor.
“Although other work has also linked cannabis to CHD, there are several potential confounders that may explain this association. Our MRI analysis suggests that this relationship may be directly causal,” Paranjpe said.
Marijuana and the heart
Why does marijuana appear to damage the heart and blood vessels? First, it increases your heart rate and blood pressure immediately after each consumption, according to the CDC.
“Marijuana smoke also releases many of the same substances that researchers have found in tobacco smoke; these substances are harmful to the lungs and cardiovascular system,” the agency says.
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 published at the time noted studies that found that heart rhythm abnormalities, such as tachycardia and atrial fibrillation, could occur within an hour after smoking marijuana containing delta-9-tetrahydrocannabinol, or THC (THC is the part of the marijuana plant that produces the psychoactive effects).
Other research has shown that marijuana smoking triggers heart attacks and increases the risk of stroke and heart failure in people with underlying heart disease.
In particular, the new study was unable to determine whether different types of cannabis use — consuming edibles or smoking marijuana, for example — influence a person’s risk of developing coronary heart disease. However, since THC reaches the brain more quickly when smoked, the researchers argue that different methods of consumption and their impact on the heart should be investigated in the future.