A habit that millions of people consider harmless could be quietly raising the odds of a heart attack. A major new review, published in The American Journal of Medicine, has pulled together years of research on cannabis use and heart attack risk, and the picture it paints is far from reassuring, especially for younger adults who assume their hearts are safe.
Cannabis use has climbed sharply over the past decade. In the United States alone, around 19% of adults, roughly 52.5 million people, reported using cannabis in 2021, more than double the figure from ten years earlier. As legalisation spreads and the drug becomes more socially accepted, doctors say the cardiovascular consequences are only now coming into focus.
A Growing Body of Evidence
The review describes cannabis use and heart attack risk as a genuine and often overlooked clinical concern, particularly among people in their twenties and thirties who have none of the usual warning signs, no high cholesterol, no diabetes, no family history. Case reports and larger population studies have repeatedly found heart attacks occurring in young, apparently healthy cannabis users shortly after they consumed the drug.
Among people already living with heart disease, the numbers are striking. Surveys of cardiac patients found that around 4% use cannabis daily and a further 7.1% use it occasionally. In people with premature atherosclerotic heart disease, meaning heart disease that strikes unusually early in life, cannabis use was reported in up to 12.5% of cases.
Why Cannabis Can Trigger a Heart Attack
The mechanisms behind marijuana and cardiovascular risk are more complicated than most people realise. Smoking or vaping cannabis activates the sympathetic nervous system, pushing up heart rate, blood pressure and the force of each heartbeat. All of this raises the heart’s demand for oxygen at the exact moment the drug is also cutting off its supply.
That happens because cannabis smoke raises levels of carboxyhemoglobin in the blood, a compound that reduces how much oxygen red blood cells can actually carry. The heart is asking for more fuel while receiving less of it, a mismatch that researchers believe helps explain why some users suffer heart attacks despite having clear, undamaged arteries.
On top of that, cannabis appears to trigger coronary vasospasm, a sudden and temporary narrowing of the arteries feeding the heart, along with damage to the delicate lining of blood vessels known as the endothelium. The drug has also been shown to activate platelets, the blood cells responsible for clotting, nudging the body towards a prothrombotic state in which clots form more easily than they should.
Not Everyone Is Affected Equally
Interestingly, not every cannabis user faces the same level of danger, and genetics appear to play a real part in that. Variation in cannabinoid receptors, the docking points cannabis compounds attach to in the body, seems to influence whether the drug’s effects lean towards harm or, in some cases, protection. Differences in how the liver enzyme CYP2C9 breaks down THC, the main psychoactive compound in cannabis, may also explain why some people are far more vulnerable than others to its cardiovascular effects.
A Complication for Heart Patients Already on Treatment
Perhaps the most immediately practical finding concerns patients recovering from a stent procedure, formally known as percutaneous coronary intervention. Data from more than 7.3 million such patients in the United States, gathered between 2004 and 2014, found that 0.4% met the criteria for cannabis misuse. Crucially, those patients were considerably younger than average, 49.5 years old compared with 64.6, and more likely to be male.
For these patients, the concerns go beyond the heart attack itself. Many are prescribed clopidogrel, a blood thinning drug designed to stop dangerous clots forming inside a newly placed stent. The review notes that cannabidiol, or CBD, blocks an enzyme called CYP2C19 that the body needs to activate clopidogrel properly. In practical terms, cannabis use could quietly undermine one of the very treatments meant to protect a patient’s heart, prompting the review’s authors to suggest doctors consider alternative medications for patients who use cannabis regularly.
The Numbers Behind the Headlines
Large population studies cited in the review found that daily cannabis use is independently linked to a 25% higher risk of heart attack, even after accounting for other lifestyle factors. That figure sits alongside a wider body of evidence connecting frequent use to elevated cardiovascular risk, although the authors are careful to note that not all long term studies agree, and more rigorous, prospective research is still needed to settle some of the more contested questions.
What This Means Going Forward
The authors are not claiming cannabis is uniquely dangerous compared with other substances, but they are pushing for something simple: better awareness. They argue that questions about cannabis use and heart attack risk deserve the same routine attention in clinics that smoking and alcohol already receive, particularly for younger patients who might otherwise be waved through without a second thought.
As legalisation continues to expand and cannabis edges further into the mainstream, understanding marijuana and cardiovascular risk is becoming less of a niche academic interest and more of an everyday clinical reality. For anyone weighing up the risks, the message from this latest research is straightforward. The heart does not necessarily distinguish between a legal habit and a dangerous one, and for some people, the consequences can arrive without warning.
(Source: WRD News)