Research suggests cannabis may offer heart health benefits, even as it remains linked to potential risks. Here’s a look at some of the interesting findings on cannabis’s effect on the heart, including how it can contribute to cardiovascular health.
Kevin Smith, director of cult films such as Clerks, Mallrats and Jay and Silent Bob Strike Back, says cannabis saved his life.
Back in 2018, the writer/director suffered a massive heart attack—the kind that only 20 percent of patients survive, that doctors call “the widowmaker.” But Smith had smoked a considerable amount of cannabis earlier in the day, and he says his doctors told him that all of that marijuana may have saved his life.
How? It isn’t completely clear—though Smith credits his consumption for keeping him calm and relaxed during his heart attack, something his doctors said kept his condition from deteriorating further.
Today, seven years later, Smith is still making movies (and he even owns a movie theater!). No word on whether he’s still consuming cannabis, but his story highlights the contradictory and often confusing evidence about cannabis’s effects on the heart.
Considerable research shows that cannabis can contribute to increased rates of heart attack and stroke, especially in people who already have some form of heart disease. However, some studies reveal some surprising discoveries about the benefits of cannabis—and tetrahydrocannabinol (THC) in particular—for a healthy heart.
What Is Cannabis’s Effect on the Heart?
The Cannabis sativa plant contains more than 100 different compounds and terpenes—oils that add flavors and scents to all plants.
Each cannabis strain has its own unique profile of cannabinoid compounds and terpenes, but they all contain significant amounts of two major cannabinoids: THC and cannabidiol (CBD). Though the proportions of CBD and THC can vary across strains, these two compounds account for many of the various effects cannabis can have on your health.
CBD has a long list of documented health benefits. It doesn’t get you high like THC, but it has been reported to help in the following ways:
- Relieve pain
- Fight inflammation
- Protect the delicate neural structures of the brain
THC is responsible for the classic marijuana euphoric high, as well as many of the potential undesirable side effects of consuming cannabis, such as these:
- Anxiety
- Paranoia
- Agitation
These compounds and others trigger receptors in the body’s endocannabinoid system (ECS), a widespread network that responds to cannabinoid chemicals produced naturally by the body as well as those from outside sources.
Here’s Where Things Get Confusing
Cannabis’s effect on the heart is not entirely straightforward, and how your body responds can depend on the method of consumption, the specific strain and the ratio of cannabinoids. While cannabis products that contain equal or proportional amounts of THC and CBD (or similar compounds) may have one set of effects, products with high levels of THC can trigger a very different response in the cardiovascular system.
Some of the common effects of cannabis on the heart and blood vessels include the following:
- Elevated blood pressure: Cannabis can cause a temporary increase in blood pressure, which may be more pronounced in people with pre-existing heart conditions.
- Rapid resting heart rate: THC can speed up the heart rate, a phenomenon known as tachycardia, which could be risky for individuals with heart problems.
- Dilated blood vessels: This effect is what causes the characteristic red eyes and flushing seen after cannabis use. While this is usually harmless, it can lead to fluctuations in blood flow, which can be more problematic for those with underlying cardiovascular issues.
Research also suggests that the risk of a heart attack or stroke may spike during the first hour after consuming cannabis, particularly if it’s smoked. This risk seems to be especially high for individuals who already have heart disease. Scientists suspect that THC is largely responsible for these heightened risks, as it can cause an increase in heart rate and blood pressure, which can be dangerous in these situations.
However, there’s another side to this story: Cannabis may also offer protective benefits for the heart in certain circumstances. Recent studies show that cannabis, specifically THC, might improve a person’s chances of surviving a heart attack or stroke. For example, research indicates that cannabis may help reduce the likelihood of developing atrial fibrillation, a type of irregular heartbeat, in people who are already experiencing heart failure.
Some studies also point to the possibility that THC and CBD may have unique cardiovascular benefits, though the mechanisms behind these effects remain unclear. The complexities of how cannabis interacts with the heart continue to be a topic of active research, and new discoveries could provide more clarity in the future.
What Causes Coronary Artery Disease?
Coronary artery disease is the most common form of heart disease, and it’s one of the leading causes of death in the US. Atherosclerosis, or “hardening of the arteries,” causes coronary artery disease. That’s a process in which plaque builds up on the walls of arteries that supply blood to the heart and brain.
Plaque is a combination of these elements:
- Cholesterol deposits
- Fatty substances
- Other kinds of cells
When all of this accumulates on artery walls, they become stiff and narrow. Over time, accumulated plaque can reduce the flow of blood or even block it entirely, causing a heart attack.
Plaque deposits can also break off and travel to other blood vessels, where they can block blood flow and cause strokes.
How Cannabis Factors Into Coronary Artery Disease
Treatment for coronary artery disease includes lifestyle changes. These include the following:
- Quitting smoking
- Performing regular exercise
- Taking powerful drugs such as beta-blockers and statins
Surgery may be needed to clear blocked arteries or place a stent to help blood flow.
But some studies also suggest that THC can affect ECS receptors in the arteries themselves to reduce the buildup of plaque.
In a study reported in the British Journal of Psychopharmacology, researchers found that people with atherosclerosis have elevated levels of a certain type of cell, called foam cells. These cells gravitate to the fatty deposits on artery walls, where they ingest low-density lipoproteins—the LDL cholesterol that’s popularly known as “bad cholesterol.” This gives them an easily identifiable foamy appearance. As they accumulate, they form the plaque that causes the narrowing and blockage of arteries.
The ECS is made up of receptors, called CB1 and CB2. These receptors are found in varying amounts throughout the body’s cells and tissues. According to research, the foam cells that cause artery plaque contain CB2 receptors. When THC activates these receptors, it appears to prevent foam cells from depositing fatty plaque on artery walls.
Low doses of THC may also protect the arteries from damage that LDL cholesterol causes. Oxidation of cells releases free radicals, toxic byproducts that can damage cells and accelerate their decay.
When LDL cholesterol oxidizes, it can produce inflammation that damages artery walls. But low doses of THC also seem to inhibit the activity of an enzyme that oxidizes LDL cholesterol. This reduces inflammation levels that contribute to coronary artery disease.
The Heart-Cannabis Connection: A Complex Relationship
Cannabis’s effect on the heart is complex, and scientists are still working to understand why cannabis can protect the cardiovascular system under some circumstances and raise the risk of heart attack and stroke in others. But recent discoveries about THC’s power to affect artery plaque could point the way to new, safer ways to protect the heart.
New Research in 2025
Recent findings, published in 2024, suggest a nuanced connection between cannabis and heart health. For instance, studies on the effects of cannabinoids on endothelial function—the ability of blood vessels to dilate and contract—show potential for therapeutic applications in improving blood flow in certain cardiovascular conditions. However, the cardiovascular risks tied to THC, such as arrhythmias and acute stress-induced responses, particularly after smoking or high doses, remain a concern.
