Yes, research links cannabis to a higher risk of heart attack: smoking it can briefly trigger one in vulnerable people, and frequent use is associated with higher heart attack rates in several large studies. The absolute risk for a healthy young adult is still low, and the evidence is observational. The risk is greatest with daily use, with smoking, and in people who already have heart disease.
This article replaces an older summary of a single 2001 Harvard study. That study still matters, but it now sits alongside national surveys of hundreds of thousands of adults, a health-records study of 4.6 million people and a 2025 meta-analysis. Here is what each found, how much weight it deserves and what to do with the information.
The Study That Started It: Heart Attacks in the Hour After Smoking
In 2001, researchers at Beth Israel Deaconess Medical Center and Harvard published the first study of cannabis as a heart attack trigger in Circulation. They interviewed 3,882 people a few days after a heart attack. Of those, 124 had smoked marijuana in the past year, 37 within 24 hours of symptoms and 9 within one hour.
Using a case-crossover design, which compares each patient’s exposure just before the heart attack with that same patient’s usual habits, they found the risk of heart attack was 4.8 times higher than baseline in the 60 minutes after smoking. The extra risk dropped quickly after that. The authors called marijuana a “rare trigger,” because so few patients had used it right beforehand.
The old version of this page said the study concluded marijuana had “little to no effect” on heart attacks. That was not the finding. The study found a real short-term rise in risk, and it remains the main evidence for the “trigger” effect. The National Academies 2017 review rated that evidence as “limited,” mainly because it rests on few cases.
What Newer, Larger Studies Found
Daily use and heart attack: 434,000 U.S. adults
A 2024 study in the Journal of the American Heart Association analyzed national survey data from 434,104 adults aged 18 to 74. After adjusting for tobacco use and other factors, daily cannabis users had 25% higher odds of having had a heart attack than nonusers. Among people who had never used tobacco, the odds were 49% higher. Risk rose with the number of days of use per month.
Adults 50 and under: 4.6 million health records
A 2025 study in JACC: Advances followed 4.6 million adults aged 50 or younger without major heart disease at the start. About 2% were cannabis users. Heart attacks occurred in 0.56% of users versus 0.09% of nonusers, a risk about six times higher. The absolute numbers are small, and users differed from nonusers in other ways, including body weight and depression, so the study shows association, not cause.
Pooled evidence: the 2025 meta-analysis
A systematic review in the journal Heart combined 24 studies and found cannabis use was associated with a 29% higher risk of acute coronary syndrome (heart attack and unstable angina), a 20% higher stroke risk and roughly double the risk of cardiovascular death. The authors noted that the studies measured cannabis exposure inconsistently and could not say whether events happened during active use.
Studies that found no link
The CARDIA study, which followed 5,113 young adults for about 27 years, found no association between lifetime or recent cannabis use and coronary heart disease by middle age. Most participants were light users, which may explain the difference from studies that capture more daily users.
Heart Attack Studies at a Glance
| Study | Size | Finding |
|---|---|---|
| Mittleman, 2001 | 3,882 heart attack patients | 4.8x risk in the hour after smoking |
| CARDIA, 2017 | 5,113 adults, 27 years | No link with mostly light use |
| Jeffers, 2024 | 434,104 adults | Daily use: 25% higher odds (49% in never-tobacco users) |
| Kamel, 2025 | 4.6 million adults 50 and under | About 6x relative risk; 0.56% vs 0.09% absolute |
| Storck, 2025 | 24 studies pooled | 29% higher acute coronary syndrome risk |
How Cannabis Could Trigger a Heart Attack
Researchers point to several mechanisms, none fully proven in people:
- Heart rate and blood pressure. THC raises heart rate and can raise blood pressure right after use, per the CDC. That raises the heart’s oxygen demand, which narrowed arteries may not be able to meet.
- Blood vessel function. A 2025 UCSF study found that both cannabis smokers and THC-edible users had impaired artery dilation, an early marker of heart disease.
- Inflammation. Stanford researchers reported that marijuana smoking activated inflammatory signals tied to heart disease, and lab work showed THC inflamed blood vessel cells. See our cannabis and atherosclerosis guide for more.
- Smoke. Combustion adds many of the same toxic substances found in tobacco smoke.
What the American Heart Association Says
The AHA’s 2020 scientific statement, “Medical Marijuana, Recreational Cannabis, and Cardiovascular Health”, concluded that cannabis has few cardiovascular benefits and many cardiovascular concerns. The AHA recommends that people not smoke or vape cannabis, citing potential harm to the heart, lungs and blood vessels. Our broader cannabis and heart health guide covers the statement in more detail.
Evidence at a Glance
| Claim | Evidence level | Source |
|---|---|---|
| Smoking cannabis can trigger a heart attack within an hour | Limited (few cases, consistent) | Mittleman 2001; National Academies 2017 |
| Daily use is linked to higher heart attack rates | Moderate (large observational studies) | Jeffers 2024; Storck 2025 |
| Young adult users have more heart attacks than nonusers | Moderate (one very large records study) | Kamel 2025 |
| Light or occasional use raises long-term heart attack risk | Mixed | CARDIA 2017 |
| Cannabis protects against heart attacks | No evidence | AHA 2020 |
Risks and Side Effects
- Racing heart, palpitations and lightheadedness, more likely at high THC doses.
- Higher heart attack risk soon after smoking, especially with existing coronary disease.
- Higher heart attack and stroke odds with daily use.
- Delayed, stronger effects from edibles, which can lead to taking too much.
- Possible interactions with heart medicines and blood thinners.
Talk to Your Doctor
If you have had a heart attack, have angina, coronary artery disease, an arrhythmia or high blood pressure, ask your cardiologist before using cannabis in any form. Be honest about how often you use it: it is part of your risk profile. If you use cannabis, the lower-risk choices are to avoid smoking, avoid daily use, keep THC doses low and never combine it with tobacco or stimulants. Chest pain, pressure, pain spreading to the arm or jaw, or shortness of breath after using cannabis needs emergency care. Call 911 and do not wait for the high to wear off.
More on the science in our cannabis research section, including cannabis and mortality.
Cannabis and Heart Attack FAQ
Can smoking weed cause a heart attack?
It can trigger one in some people, mostly those with existing heart disease. One study found risk was 4.8 times higher in the hour after smoking. Frequent use is also linked to more heart attacks over time.
How long after smoking weed is heart attack risk highest?
In the main study on timing, the risk was highest in the first hour after smoking and fell quickly after that.
Can young people have a heart attack from marijuana?
It is uncommon, but a 2025 study of adults 50 and under found heart attacks were about six times more common in cannabis users, at 0.56% versus 0.09%.
Is it safe to use cannabis after a heart attack?
There is no good evidence that it is safe, and the known effects on heart rate and blood pressure are a concern. Ask your cardiologist before using any cannabis product.
Do edibles carry the same heart attack risk as smoking?
Probably less from smoke-related harm, but not zero. THC still raises heart rate, and a 2025 study found impaired blood vessel function in edible users.
For adults 21+ in legal states. General information, not medical advice. Talk to a doctor before using cannabis for a health condition.