There is no good evidence that cannabis prevents or slows atherosclerosis in people; the human studies range from no effect at light use to signs of artery damage with heavier use. A widely cited 2005 study found low-dose THC slowed plaque growth in mice, but later lab work found THC can also inflame blood vessels, and human data point toward risk rather than protection.
Atherosclerosis is the buildup of fatty, inflamed plaque inside artery walls. It is the main cause of heart attacks and most strokes. Because the body’s endocannabinoid system helps regulate inflammation, scientists have spent two decades asking whether cannabis compounds make it better or worse. The answer so far depends heavily on what was studied: mice, cells or people. This page, which once covered only the 2005 mouse study, now covers the full body of research.
The 2005 Mouse Study: Why It Got Attention
In 2005, researchers in Geneva published a study in Nature showing that oral THC at 1 mg per kg per day slowed the progression of atherosclerosis in mice bred to develop it. The dose was lower than what usually causes a high. Immune cells from treated mice were less active, and the benefit disappeared when the scientists blocked the CB2 receptor, the cannabinoid receptor found mainly on immune cells. They also found CB2 receptors in human and mouse plaques.
The study was important for showing that the endocannabinoid system plays a role in artery inflammation. It did not show that smoking or eating cannabis protects human arteries. Mouse models of atherosclerosis differ from human disease, the THC was given in controlled oral doses, and the effect ran through CB2, while THC also strongly activates CB1 receptors, which have different effects. (The old version of this page also wrongly linked the study to ALS. It was about atherosclerosis only.)
Later Lab Research Points the Other Way
A 2022 Stanford study in Cell reached a less reassuring conclusion. The team reported that marijuana smoking activated inflammatory signals linked to heart disease, and that THC triggered inflammation and oxidative stress in human blood vessel cells grown from stem cells. Blocking the CB1 receptor reduced those effects, and genistein, a soybean compound that acts as a CB1 blocker, reduced THC-related plaque and blood vessel dysfunction in mice. The same paper cited UK Biobank data identifying cannabis as a cardiovascular risk factor.
Later mouse work has continued to focus on CB1. A 2026 study in Nature Communications reported that mice lacking CB1 receptors in the artery lining had less arterial inflammation and lipid uptake. Together these findings suggest the two receptors may pull in opposite directions, and THC acts on both.
What Human Studies Show
The best long-term human data come from CARDIA, a U.S. study that has followed thousands of adults since they were 18 to 30 years old in 1985 and 1986.
- Artery calcium (2018). Among 3,117 participants scanned at year 25, cumulative cannabis use was not linked to coronary or abdominal artery calcium in people who never smoked tobacco. In people who had smoked tobacco, five “marijuana-years” of use was linked to roughly double the odds of artery calcium.
- Carotid artery thickness (2021). In 3,257 participants, cannabis use showed no association with thicker carotid artery walls, while tobacco showed a strong one.
- Heart disease events (2017). CARDIA found no link between cannabis use and cardiovascular events by middle age.
A key caveat: CARDIA participants mostly used cannabis lightly. Only 6% of users in the calcium analysis reported ever using it daily.
Studies of heavier and more recent users look different. A 2025 UCSF study found impaired artery dilation in both chronic smokers and THC-edible users, a change that typically comes before plaque buildup. Large outcome studies, including a 434,000-person AHA journal study and a 2025 meta-analysis, link frequent cannabis use to more heart attacks and strokes, the main end results of atherosclerosis.
Mice vs Humans: Why the Results Differ
| Factor | 2005 mouse study | Real-world cannabis use |
|---|---|---|
| Form | Pure oral THC | Often smoked, with combustion products |
| Dose | Low, controlled, daily | Variable and often high-potency |
| Receptor focus | CB2 (immune cells) | THC also activates CB1, linked to vessel inflammation |
| Other exposures | None | Tobacco, alcohol and diet often differ in users |
| Outcome measured | Plaque size in mice | Calcium, artery function, heart attacks, strokes |
The American Heart Association’s View
The AHA’s 2020 scientific statement, “Medical Marijuana, Recreational Cannabis, and Cardiovascular Health”, found that cannabis has few cardiovascular benefits and that many of its health concerns are cardiovascular. The AHA recommends against smoking or vaping cannabis. It does not recommend any cannabis product for preventing or treating atherosclerosis.
Evidence at a Glance
| Claim | Evidence level | Source |
|---|---|---|
| Low-dose oral THC slows plaque growth in mice via CB2 | Animal study only | Steffens 2005 |
| THC inflames blood vessel cells via CB1 | Lab and animal studies | Wei 2022 |
| Light cannabis use is linked to artery calcium or thickness | Mixed; no link in never-tobacco users | CARDIA 2018, 2021 |
| Chronic use impairs artery function | Limited (small study) | UCSF 2025 |
| Cannabis prevents atherosclerosis in people | No evidence | AHA 2020 |
Risks and Side Effects
- Artery inflammation and impaired blood vessel function in lab and early human studies.
- Higher heart attack and stroke rates with frequent use in observational studies. See cannabis and heart attack risk.
- Added risk when combined with tobacco, the group in which CARDIA found a calcium link.
- Faster heart rate and higher blood pressure right after use, per the CDC.
Talk to Your Doctor
If you have atherosclerosis, high cholesterol, a high calcium score or a family history of early heart disease, cannabis is not a treatment, and it may add risk. Proven steps such as statins when prescribed, blood pressure control, quitting tobacco and exercise have strong evidence. Tell your doctor if you use cannabis and how often, especially if you smoke it or also use tobacco. For the bigger picture, read our cannabis and heart health guide and browse the research section.
Cannabis and Atherosclerosis FAQ
Does marijuana clog your arteries?
The evidence is mixed. Long-term U.S. data found no link with light use in people who never smoked tobacco, but cannabis was linked to artery calcium in tobacco smokers, and newer studies link heavier use to artery dysfunction and more heart attacks.
Can THC reverse atherosclerosis?
No. A 2005 study found low-dose THC slowed plaque growth in mice, but it has never been shown in people, and later lab work found THC can inflame blood vessels.
Does CBD help with atherosclerosis?
There is no human evidence that CBD prevents or treats atherosclerosis. Any suggested benefits come from lab or animal work.
Is smoking weed as bad for arteries as smoking cigarettes?
Not on the same evidence. In CARDIA, tobacco was strongly linked to artery calcium and thickness, while light cannabis use was not. But one 2025 study found artery function in chronic cannabis users was impaired to a degree similar to tobacco smokers.
What is genistein and why is it in cannabis research?
Genistein is a soybean compound that Stanford researchers found blocks the CB1 receptor and reduced THC-driven vessel inflammation in lab and mouse studies. It has not been tested for this purpose in people.
For adults 21+ in legal states. General information, not medical advice. Talk to a doctor before using cannabis for a health condition.
