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A new study has found a startling link between chronic cannabis use and increased risk of cardiovascular disease—regardless of whether you smoke it or consume edibles. The finding challenges commonly held beliefs about the health impacts of tetrahydrocannabinol (THC), which many see as a relatively harmless drug—especially when ingested.
The study, published Wednesday, May 28 in the journal JAMA Cardiology, found that THC smokers suffer from significantly worse artery function than non-users. They observed the same effect in edible consumers, though their arteries were not as severely affected. In either case, vascular function was reduced by roughly half compared to those who do not use cannabis, according to a statement from the University of California, San Francisco.
“Scientifically, this THC result is really interesting but boy does it screw up the public health messaging,’” co-author Matt Springer, a cardiovascular researcher at UCSF, reportedly said to lead author and UCSF physician-scientist Leila Mohammadi when he saw the data.
These results add to a growing body of evidence that suggests long-term weed use can lead to cardiovascular damage and life-threatening events such as heart attacks and strokes, though experts still lack consensus on its precise impacts. A 2024 study published in the Journal of the American Heart Association found that people who consume cannabis daily had a 25% increased risk of heart attack and a 42% increased risk of stroke compared to non-users.
For this new study, researchers investigated how cannabis impacts vascular function. To isolate the effects of chronic cannabis use, they recruited 55 otherwise healthy adults aged 18 to 50 who did not use any form of nicotine and were not frequently exposed to secondhand smoke.
These participants were sorted into three groups: marijuana smokers, edible users, and non-users. Those in the two cannabis user groups reported taking the drug at least three times per week, either exclusively through smoking or edibles.
To assess the participants’ vascular function, the researchers measured dilation of the brachial artery—located in the upper arm—to determine whether it could properly expand in response to increased blood flow. To that end, they used an inflatable forearm cuff to briefly block blood flow to the artery, then used ultrasound to measure its diameter before and after inflating the cuff.
Matt Springer, a cardiovascular researcher at UCSF whose lab led the study, told Live Science that his test offers a “window into the future.” When blood vessels cannot fully dilate, he said, the risk of heart attack and other poor cardiovascular outcomes increases.
Participants who did not consume cannabis showed an average vessel dilation—represented as the percent change from the baseline measurement of artery diameter—of 10.4%. This value was significantly reduced among weed smokers and edible users, who showed an average vessel dilation of 6.0% and 4.6%, respectively. For reference, average values for brachial artery dilation in healthy individuals typically range from 8.0% to 15%. In a previous study, Springer’s lab found similarly reduced levels of vessel dilation among e-cigarette and cigarette smokers.
To better understand how THC causes this change, the researchers ran lab tests to determine how endothelial cells—which form the linings of blood vessels and release nitric oxide to trigger dilation—responded to the participants’ blood samples. These tests revealed that the blood of chronic cannabis smokers inhibited nitric oxide production in the cells, which may explain why these participants showed reduced vessel dilation.
This effect was not observed in edible consumers, however, suggesting that ingestible THC may impact arterial function via an entirely separate mechanism. Figuring out what that mechanism may be will require further research. What’s more, subsequent studies will need to reproduce these findings in a larger population to validate the results.
Within the last several years, cannabis use among U.S. adults has reached new heights, according to the NIH’s National Institute on Drug Abuse. As such, investigating the health effects of THC is more important than ever before—especially as mounting evidence challenges perceptions of weed as a harmless high.
“}]] The research adds to a growing body of evidence that suggests weed may not be as safe as people think it is. Read More
