Chronic cannabis use may impair blood vessel function in otherwise healthy young adults, according to a new study that examined vascular health among marijuana smokers, tetrahydrocannabinol-edible users, and nonusers.
Researchers found that both marijuana smoking and tetrahydrocannabinol (THC) ingestion were associated with reduced flow-mediated dilation (FMD), a key marker of endothelial function. Lower FMD indicates reduced ability of blood vessels to dilate, an early sign of cardiovascular risk.
In the study, the researchers enrolled 55 healthy adults aged 18 to 50 years. The participants were divided into three groups: chronic marijuana smokers, THC-edible users, and nonusers. Cannabis users reported using marijuana or THC edibles at least three times per week for 1 year or more. None of the participants smoked tobacco, vaped, or were regularly exposed to secondhand smoke, minimizing potential confounding exposures.
FMD measurements showed a mean of 6.0% (standard deviation [SD] = 2.6%) in marijuana smokers and 4.6% (SD = 3.7%) in THC-edible users compared with 10.4% (SD = 5.2%) in nonusers. FMD was inversely correlated with both smoking frequency (r = −0.7, P < .001) and THC dose from edibles (r = −0.7, P = .03), indicating that higher cannabis use was linked to greater impairment.
To explore biological mechanisms, the researchers conducted cell-based assays using serum samples from the participants. They exposed human umbilical vein endothelial cells to each serum sample and stimulated the cells with vascular endothelial growth factor. Cells treated with serum from marijuana smokers released less nitric oxide—an important molecule for vascular dilation—compared with those treated with serum from nonusers. This effect wasn't observed in cells exposed to serum from THC-edible users, suggesting differing impacts based on the mode of cannabis consumption.
Other vascular measures, including pulse wave velocity and arterial stiffness, didn't differ significantly between the groups. Blood pressure, cholesterol, triglycerides, and other health markers were also similar across the participants.
To ensure accuracy, the researchers confirmed cannabis use through both self-reported methods and laboratory testing for THC metabolites in the blood and urine. They used standardized imaging tools to measure vascular responses and applied appropriate statistical methods to compare the results across the groups.
While the researchers didn't evaluate long-term clinical outcomes such as heart attacks or strokes, the observed reduction in FMD pointed to early endothelial dysfunction in cannabis users. The findings contributed to ongoing research on the cardiovascular effects of cannabis, particularly as legalization and usage rates continue to rise.
The researchers emphasized the need for further longitudinal studies to determine whether these early vascular changes are predictive of future cardiovascular events.
The study was conducted in California and supported by funding from public health and scientific research organizations.
Full disclosures can be found in the published study.
Source: JAMA Cardiology