Although cannabis may have therapeutic benefits, improving cardiovascular health does not appear to be one of them.
In a scientific paper released on Wednesday, the American Heart Association (AHA) warns that research to date has found no cardiovascular benefits from the use of cannabis (marijuana), but some studies have identified “substantial risks,” including an increased risk of heart attacks and strokes.
Those studies have been primarily observational, however, so they can’t prove cause and effect. Citing an “urgent need” for more rigorous research on cannabis use and cardiovascular health, the authors of the AHA paper call on the federal government to end the classification of cannabis as a Schedule I drug, which currently hinders the ability of scientists to study it.
“We urgently need carefully designed, prospective short- and long-term studies regarding cannabis use and cardiovascular safety as it becomes increasingly available and more widely used. The public needs fact-based, valid scientific information about cannabis’s effect on the heart and blood vessels,” says Robert Page, the paper’s lead author and a professor of clinical pharmacy at the University of Colorado, in a released statement.
A tale of two chemicals
For the new paper, Page and his colleagues searched the medical literature for evidence of the effects of cannabis on the cardiovascular system. They found a lot to be concerned about.
One recent study, for example, reported that 6 percent of heart attack patients under the age of 50 are frequent cannabis users. Another found that young adults (people aged aged 18 to 44) who smoke marijuana (but not cigarettes) more than 10 days a month are 2.5 times more likely to have a stroke than non-users.
Cannabis use has also been linked to an increased risk of various heart irregularities (such as atrial fibrillation) and heart failure. And hospitals in states that have legalized cannabis have seen increases in emergency department visits and admissions for heart attacks.
Again, these are observational studies, so they can’t prove cause and effect.
Evidence suggests biological explanations for such findings, however. Scientists report that one of the main chemicals in cannabis — THC (tetrahydrocannabinol), which produces the plant’s “high” — appears to trigger the body’s “fight or flight” response, which leads to a higher heart rate, a greater demand for oxygen by the heart, higher blood pressure while lying down and dysfunction within the walls of the arteries.
Interestingly, CBD (cannabidiol) — another key chemical in cannabis, but one that doesn’t produce a “high” — seems to have none of those negative effects. In fact, research has associated CBD with reduced heart rate, lower blood pressure and increased vasodilation (the ability of arteries to remain open).
Yet, of the dozens of cannabis products currently available in the United States, the Food and Drug Administration has approved only one derived from CBD, Page and his co-authors point out.
Inhaling adds more dangers
As the paper’s authors also note, smoking and inhaling cannabis, no matter what its THC content, produces many of the same dangers as smoking tobacco. It increases blood concentrations of carbon monoxide (a poisonous gas) fivefold and those of tar (partially burnt combustible matter) threefold — levels similar to those associated with inhaling tobacco smoke.
In addition, vaping cannabis, particularly when the cannabis is mixed with vitamin E acetate oils, has been linked to a sometimes fatal illness known as EVALI (e-cigarette or vaping product use-associated lung injury).
“People who use cannabis need to know there are potentially serious health risks in smoking or vaping it, just like tobacco smoke,” says Dr. Rose Marie Robertson, chief science officer for the AHA, in a released statement. “The American Heart Association recommends that people not smoke or vape any substance, including cannabis products, because of the potential harm to the heart, lungs and blood vessels.”
“If people choose to use cannabis for its medicinal or recreational effects, the oral and topical forms, for which doses can be measured, may reduce some of the potential harms,” stresses Page.
“It is also vitally important that people only use legal cannabis products because there are no controls on the quality or the contents of cannabis products sold on the street,” he adds.