Cannabis Use Shows Substantial Risks, No Benefits for Cardiovascular Health

Marijuana Various

Marijuana. Credit: Copyright American Heart Association

  • Observational studies have found no cardiovascular benefits associated with cannabis use.
  • Cannabis use may be linked to an increased risk of heart attacks, atrial fibrillation, and heart failure; however, additional studies need to be conducted to better understand the research findings.
  • Cannabis is classified as a Schedule I drug by the U.S. Drug Enforcement Agency (DEA), which severely limits scientists from studying it.

The chemicals in cannabis have been linked to an increased risk of heart attacks, heart failure, and atrial fibrillation in observational studies; however, a full understanding of how use of cannabis affects the heart and blood vessels is limited by a lack of adequate research, according to a new Scientific Statement from the American Heart Association (AHA) published today in its flagship journal Circulation.

According to the statement, although cannabis, also known as marijuana, may be helpful for conditions such as spasticity associated with multiple sclerosis, among others, cannabis does not appear to have any well-documented benefits for the prevention or treatment of cardiovascular diseases. Preliminary studies have found that cannabis use could negatively impact the heart and blood vessels.

Dried Marijuana Cigarette

Marijuana Cigarette. Credit: Copyright American Heart Association

“Attitudes towards recreational and medicinal use of cannabis have changed rapidly, and many states have legalized it for medical and/or recreational use. Health care professionals need a greater understanding of the health implications of cannabis, which has the potential to interfere with prescribed medications and/or trigger cardiovascular conditions or events, such as heart attacks and strokes,” said Robert L. Page II, Pharm.D., M.S.P.H., FAHA, chair of the writing group for the statement and professor in the department of clinical pharmacy and the department of physical medicine/rehabilitation at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences in Aurora, Colorado.

A recent study cited in the statement suggests that cannabis use is present in 6% of heart attack patients under 50 years of age. Another study found that cannabis users ages 18 to 44 had a significantly higher risk of having a stroke compared to non-users. “Unfortunately, most of the available data are short-term, observational, and retrospective studies, which identify trends but do not prove cause and effect,” said Page.

The most common chemicals in cannabis include THC (tetrahydrocannabinolic acid), the component of the plant that induces a “high,” and CBD (cannabidiol), which can be purchased over the counter, but to date, the FDA has only approved one CBD-derived product. Importantly, the FDA has not approved any other cannabis, cannabis-derived, or cannabidiol (CBD) products currently available on the market.

Robert L. Page

Robert L. Page II Pharm.D. M.S.P.H. FAHA. Chair of the writing group for the statement and professor in the department of clinical pharmacy and the department of physical medicine/rehabilitation at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences in Aurora, Colorado. Credit: Copyright University of Colorado

Some studies have found that within an hour after cannabis is smoked, THC may induce heart rhythm abnormalities, such as tachycardia, premature ventricular contractions, atrial fibrillation, and ventricular arrhythmias. Acutely, THC also appears to stimulate the sympathetic nervous system, which is responsible for the “fight or flight” response, resulting in a higher heart rate, a greater demand for oxygen by the heart, higher blood pressure while laying down, and dysfunction within the walls of the arteries.

In contrast, studies on CBD, which does not produce a “high” or intoxication, have found associations with reduced heart rate, lower blood pressure, increased vasodilation (ability of the arteries to open), lower blood pressure, and potentially reduced inflammation. Inflammation is linked to atherosclerosis, the slow narrowing of the arteries that underlies most heart attacks and, possibly strokes.

Smoking and inhaling cannabis, regardless of THC content, has been associated with cardiomyopathy (heart muscle dysfunction), angina (chest pain), heart attacks, heart rhythm disturbances, sudden cardiac death, and other serious cardiovascular conditions. In states where cannabis has been legalized, an increase in hospitalizations and emergency department visits for heart attacks has been observed.

The way cannabis is consumed may influence how it affects the heart and blood vessels. “Many consumers and health care professionals don’t realize that cannabis smoke contains components similar to tobacco smoke,” said Page. Smoking and inhaling cannabis, regardless of THC content, has been shown to increase the concentrations of blood carboxyhemoglobin (carbon monoxide, a poisonous gas) five-fold, and a three-fold increase in tar (partly burnt combustible matter), similar to the effects of inhaling a tobacco cigarette.

Carbon monoxide intoxication from inhaled tobacco or cannabis has been associated with several heart problems, such as heart muscle disease, chest pain, heart attacks, heart rhythm disturbances, and other serious conditions.

Cannabis use should be discussed in detail with a health care professional so that an individual’s potential health risks can be reviewed. “If people choose to use cannabis for its medicinal or recreational effects, the oral and topical forms, for which doses can be measured, may reduce some of the potential harms. It is also vitally important that people only use legal cannabis products because there are no controls on the quality or the contents of cannabis products sold on the street,” said Page.

In addition to the poisonous compounds in cannabis smoke, vaping cannabis may also result in serious health outcomes, especially when it is mixed with vitamin E acetate oils, which are linked to EVALI (e-cigarette or vaping product use-associated lung injury), the potentially fatal illness that emerged among e-cigarette users last year.

“People who use cannabis need to know there are potentially serious health risks in smoking or vaping it, just like tobacco smoke. The American Heart Association recommends that people not smoke or vape any substance, including cannabis products, because of the potential harm to the heart, lungs, and blood vessels,” said Rose Marie Robertson, M.D., FAHA, the deputy chief science and medical officer for the American Heart Association and co-director of the AHA Tobacco Center for Regulatory Science.

The statement also discusses cannabis use among older adults, people diagnosed with cardiovascular diseases and other populations including youth. Some studies have suggested that cannabis use – both CBD and THC – may be safe and effective for older populations. Though they are the least likely to use cannabis, older adults often use it to reduce neuropathic pain (common among people with type 2 diabetes), improve quality of life, and decrease prescription drug use (including opioids).

Additionally, benefits for patients with age-related diseases, including Parkinson’s and Alzheimer’s, have also been reported in some studies; however, there is very little research on the long-term effects of cannabis use among this group of people. Another concern about older adults using cannabis is the potential of interactions with other medications, including blood thinners (anti-coagulants), anti-depressants, antipsychotics, antiarrhythmics for heart rhythm abnormalities, and statin drugs, which reduce cholesterol levels.

For people diagnosed with heart disease, cannabis should be used with extreme caution because cannabis increases the heart’s need for oxygen at the same time as it decreases the available oxygen supply, which could cause angina (chest pain). In addition, in some studies, cannabis triggered a heart attack in people with underlying heart disease. Other studies have linked cannabis use to a higher risk of strokes and heart failure.

Research into the effects of cannabis on the heart and blood vessels has been limited because cannabis is categorized as a Schedule I controlled substance by the U.S. Drug Enforcement Agency (DEA). Schedule I controlled substances are defined as having no accepted medical use, a high potential for abuse, and an unacceptable safety profile. The AHA’s Scientific Statement suggests that the DEA remove cannabis from the Schedule I of the U.S. Controlled Substances Act so that it can be widely studied by scientists. Forty-seven U.S. states, the District of Columbia, and 4 of 5 U.S. territories allow some form of cannabis use, and its use has risen considerably over the past decade, particularly among people 18-25 years of age. Although many states have legalized medical and/or recreational cannabis use, cannabis growing, sales, and use are illegal at the federal level, further complicating scientific research.

“We urgently need carefully designed, prospective short- and long-term studies regarding cannabis use and cardiovascular safety as it becomes increasingly available and more widely used,” Page said. “The public needs fact-based, valid scientific information about cannabis’s effect on the heart and blood vessels. Research funding at federal and state levels must be increased to match the expansion of cannabis use – to clarify the potential therapeutic properties and to help us better understand the cardiovascular and public health implications of frequent cannabis use.”

Legalization of cannabis for medical purposes should align with patient safety and efficacy. Legalization for recreational use will remain a significant concern until more research can be conducted on the safety and long-term population health effects across the life course and the equity and social justice impact of these laws. In those states where cannabis is legal for recreational or medical purposes, there should be a robust public health infrastructure that is adequately funded and implemented to minimize its impact on CVD mortality, especially among young people who have heart disease. The statement calls for the federal government to create standardized labeling about the amount of THC and CBD and require it on all legal cannabis products.

The Association believes cannabis should be tightly integrated into comprehensive tobacco control and prevention efforts that include age restrictions for purchasing, retailer compliance, excise taxes, comprehensive smoke-free air laws, professional education, screening within the clinical environment – for example, when a patient is admitted to the hospital and routinely screened to avoid medication interactions or potential toxicity – and coverage of cessation treatment programs by insurers, Medicare and Medicaid. These efforts should be adequately funded, and at least some portion of the revenue from cannabis taxation should be directed toward programs and services that improve public health.

The statement was written on behalf of the American Heart Association’s Clinical Pharmacology and Heart Failure and Transplantation Committees of the Council on Clinical Cardiology; the Council on Basic Cardiovascular Sciences; the Council on Cardiovascular and Stroke Nursing; the Council on Epidemiology and Prevention; the Council on Lifestyle and Cardiometabolic Health; and the Council on Quality of Care and Outcomes Research.

Reference: “Medical Marijuana, Recreational Cannabis, and Cardiovascular Health: A Scientific Statement From the American Heart Association” by Robert L. Page II, Larry A. Allen, Robert A. Kloner, Colin R. Carriker, Catherine Martel, Alanna A. Morris, Mariann R. Piano, Jamal S. Rana, Jorge F. Saucedo, and On behalf of the American Heart Association Clinical Pharmacology Committee and Heart Failure and Transplantation Committee of the Council on Clinical Cardiology; Council on Basic Cardiovascular Sciences; Council on Cardiovascular and Stroke Nursing; Council on Epidemiology and Prevention; Council on Lifestyle and Cardiometabolic Health; and Council on Quality of Care and Outcomes Research, 5 August 2020, Circulation.
DOI: 10.1161/CIR.0000000000000883

Co-authors are Larry A. Allen, M.D., M.H.S., FAHA, (vice chair); Robert A. Kloner, M.D., Ph.D.; Colin R. Carriker, Ph.D.; Catherine Martel, Ph.D.; Alanna A. Morris, M.D., M.Sc., FAHA; Mariann R. Piano, R.N., Ph.D., FAHA; Jamal S. Rana, M.D., Ph.D.; Jorge F. Saucedo, M.D., FAHA. Author disclosures are in the manuscript.

5 Comments on "Cannabis Use Shows Substantial Risks, No Benefits for Cardiovascular Health"

  1. WOW! It’s 2020 and our government still hasn’t figured out what with pot? Go ask the pot heads and find out! First of all with the hydro type of pot there is an extreme rush one may get when one smokes it after not smoking it for the last 3-6 days. People with health conditions have to be careful because the high can send the body through stages of actions that can increase heart rate, anxiety, fear of being too high, heart pulsations, flushes, sweats and more. It seems that maybe diabetics may have problems with their blood sugar and may experience some adverse effects when smoking pot when they haven’t for a while. People who smoke pot a lot don’t get that kind of a high that someone gets one they smoke only every so often. It’s like the body builds up a resistance to getting super high as you smoke pot more. Pot smokers rarely get deadly sick from pot and most medical episodes caused by pot go away after an hour or so after one comes down from the extreme high of the pot. From what I know there has been no noticeable amount of pot smokers ending up with lung cancer or other medical problems from pot. It will make you lazy but that isn’t a medical problem. Pot just makes one want to sit back and enjoy the moment. Find out more at

  2. Carolyn L Zaremba | August 5, 2020 at 11:56 am | Reply

    I started smoking pot in the 1960s and still do on occasion. This article first declares that cannabis causes heart problems, but immediately follows that declaration with the fact that they are not allowed to research it!! Am I supposed to believe this nonsense? Studies in other countries have found many benefits to cannabis use. This article smells like anti-pot propaganda to me.

  3. I think there are many laboratory tests that directly show exactly how smoking affects the cardiovascular system. In fact, any smoking has this effect on a person. Therefore, it is very important to read more information. That the time spent smoking cannabis is much less than smoking cigarettes, despite all the claims.

  4. I know of 3 people that had psychological issues with Marijuana. They were able to quit taking their medically prescribed anti depressant and smoke weed instead. With positive results over the past 8 years, no mental breaks, no more trips to the psyche ward, less ups and downs emotionally, anxiety kept in check so Ativan was no longer needed. Lastly, a separate case than fore mentioned, I am able to cope with my ADD amd anxiety problems. Which I had a very hard time,with befote I,started smoking marijuana daily, a short 27 years ago. Smokimg joints and,pipes bongs etc do hurt the lungs. Vaping weed is only thc and cbd in the vapors and are fully absorbed into lungs. So no adverse affects. At least that’s what,doctors have said. National geographic drugs inc episode 1 delved into the science of marijuana and how it chemically affects your brain lungs body as a whole. Im fact, we naturally produce a type of cannaboid im our brains. Its what allows us to forget. Without it, you will overload from remembering every single second in its entirety without fail, day in and day out. If marijuana screws up your life so bad that you need treatment, you would,habe screwed your life up over cheeseburgers or comic collecting, or from watching TV. Basically, if it wasnt weed it would be any other number of things. Thank you for sitting through this all. Habe a goodnight. Im going to go poke some smot right now and read my book

  5. “Scientists” claim that “pot” is more potent now-a-days, and that is a problem. NO! That is the solution! People smoke until they are happy with the feeling they get. Smoke a “cigarrette” full of “pot”? Not these days; just a little pinch. Chain smoke “pot”? HA! HA! NO! Less carbon monoxide, tar, etc. I think if smoking “pot” created all these health problems, we would know by now, because SO MANY PEOPLE smoke it, recreationally, legally now-a-days or illegally for many decades. I know old folks who are 80 who grow it and smoke it every day, have for 60 years, and they are doing just fine. They smoke much more than me. That old man had skin cancer, and this medicinal herb got him through the worst of the radiation treatments. If he had underlying health problems due to smoking this herb, the docs would have caught it before they started treating him. Big Pharma is the largest industry in the world, by far (10-100 times bigger) than the next biggest: military. They have a BIG interest in keeping this MEDICINAL HERB illegal, scary, and black-listed, and fund these BS scare-tactic “studies” which manipulate the presentation of “statistics” to look bad.

    I also find it interesting that in the past, it was said that THC relaxes the blood capillaries. That is why you get “red eyes” when you smoke. It also makes it easier to absorb oxygen in the lungs. Also less stress on the heart, but it would have to pump a bit faster to keep the flow rate up (simple hydrodynamic physics). This affect in the lungs, combined with the “expectorant” effect of smoking “pot” (tickles my throat making me cough a bit), also allows lungs to clean themselves better of the toxins that are inhaled, the worst of which is industrial air pollution. When I’m in the big city or driving the interstate highways for hours, or even get behind a truck belching black smoke for 2 minutes, I cough up black speckles immediately after the first or second puff of “pot”. Then nothing. I can smoke 2-3 times my normal amount when on vacation in the countryside where the air is clean(er), and for MONTHS I cough up only clear. Back to the city, and within a day, the black speckles are back. I should mention that I have had congested lungs since I was 10, years before I ever even knew about “pot”, likely due to air pollution, second hand cigarette smoke I was exposed to as a baby (love my Grandma who took care of me then, but she was a chimney), and then likely all the antibiotics the docs gave me that did nothing to help me, but likely fed the yeast-fungal growth on my nasal and lungs’ mucus membranes that plagues me to this day. I quit going to “doctors” and am much healthier now that I don’t take their drugs that they get kickbacks for (remember, docs are taught very little about how the body works (it is way too complicated for 4 years of college) and are basically taught to remember and correlate symptoms with the drugs that suppress the symptoms).

    Cigarettes on the other hand, restrict the blood capillaries, reducing O2 levels in the body, raising blood pressure, stressing the heart to push the blood through the tighter passages, etc. And then there is the nasty chemicals that the tobacco industry adds to their cigarettes to give them the “custom” taste (etc.) for each product. I tried cigs in high school. SO NASTY! Burned my throat making me gag and cough violently! Made me feel sick. Two weeks later, I tried “pot” and only sweetness! I knew then that cigs were not for me! If people smoke a cig in my car with the windows _down_, my eyes burn, my lungs choke, my nose wants to sneeze with irritation. However, if someone smokes an American Spirit all natural “organic” hand-rolled cig in my car with the windows _up_, I don’t hardly even notice.

    “Scientists” keep releasing “studies” that describe “pot” in terms of cigs and alcohol (poisons). Don’t let them fool you.

    We know people die from opiates, have other health and mental problems from other drugs, INCLUDING THE MOST NOTORIOUS OF ALL DRUGS, *** SUGAR ***. It is in the news every day, week, year. When was the last time you heard of someone overdosing on “pot”? Dying of lung problems from smoking “pot”? Killing a child in another car because they were DUI of “pot” and swerved into another lane uncontrollably? Have to have a foot or lower leg cut off because diabetes induced from “pot” “killed” it? My nephew got into meth and broke into a building due to “temporary insanity” (his words). He graduated top of his HS class. Was doing great in college. Now he can’t function or hold a job. My cousin’s wife told me she was an ex-meth head. One of her friends showed up one night at 2AM with his imaginary friends to play pool on an imaginary pool table in her living room, all the time having a conversation with them (she had to play along or risk “upsetting” him and was warning me to stay away from that sh*t). When is the last time you heard stories like this about “pot”? NEVER. IT IS MEDICINE FOR THE MIND, BODY, EMOTIONS, AND SPIRIT. The people who divide and conquer don’t like that.

    These “studies” that “hint” of bad things about “pot” may make good headlines, but they hold no water.

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