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Cannabis may be linked to strokes and heart rhythm disturbances in young people

  • Young people who reported using cannabis frequently had higher risk of having a stroke, according to a Virginia study.
  • The risk of being hospitalized for arrhythmia was significantly greater among people diagnosed with cannabis use disorder, according to an Oklahoma study.

Embargoed until 4 a.m. CT/5 a.m. ET Monday, Nov. 11, 2019

DALLAS, Nov. 11, 2019 — Frequent cannabis (marijuana) use among young people was linked to an increased risk of stroke and people diagnosed with cannabis use disorder were more likely to be hospitalized for heart rhythm disturbances (arrhythmias), according to two new preliminary studies to be presented at the American Heart Association’s Scientific Sessions 2019 — November 16 -18 in Philadelphia. The Association’s Scientific Sessions is an annual, premier global exchange of the latest advances in cardiovascular science for researchers and clinicians. In addition, the study linking cannabis use disorder to an increased risk of stroke (Oral Presentation 333) will be published in Stroke, a Journal of the American Stroke Association, a division of the American Heart Association.

The American Heart Association does not have a position regarding legalizing cannabis, however, in locations where cannabis is legal, the Association notes that there should be a public health infrastructure in place that integrates the use of cannabis into comprehensive tobacco control efforts such as age restrictions for purchasing, comprehensive smoke- free air laws and other measures.

“As these products become increasingly used across the country, getting clearer, scientifically rigorous data is going to be important as we try to understand the overall health effects of cannabis,” said Robert Harrington, M.D., president of the American Heart Association and the Arthur L. Bloomfield professor of medicine and chairman of the department of medicine at Stanford University in Stanford, California.

Stroke risk may be higher among young cannabis users (Oral Presentation 333)

Young people who used cannabis frequently and also smoked cigarettes or used e-cigarettes were three times more likely to have a stroke compared to non-users.

The study also showed that cannabis users who did not use tobacco products but reported using cannabis for more than 10 days a month were nearly 2.5 times more likely to have a stroke compared to non-users.

The cannabis users were also more likely to be heavy drinkers, current cigarette users and e-cigarette users, which may have also influenced their risk, even though the researchers adjusted for those factors in their analysis.

Participants in the study included more than 43,000 adults aged 18 to 44, of whom nearly 14% reported using cannabis in the last 30 days. Compared with non-users, marijuana users were often younger, non-Hispanic white or black, were less likely to be college graduates and were often physically active.

“Young cannabis users, especially those who use tobacco and have other risk factors for strokes, such as high blood pressure, should understand that they may be raising their risk of having a stroke at a young age,” said lead study author Tarang Parekh, M.B.B.S., M.S., a health policy researcher at George Mason University in Fairfax, Virginia. “Physicians should ask patients if they use cannabis and counsel them about its potential stroke risk as part of regular doctor visits.”

The study was observational and did not examine the biological mechanism connection between stroke and cannabis use, so it identified a potential link, rather than proving cause and effect. The data analyzed was from the behavioral risk factor surveillance system (BRFSS) (2016-17), a nationally representative cross-sectional survey collected by the U.S. Centers for Disease Control and Prevention.

Co-authors are Sahithi Pemmasani, M.B.B.S., and Rupak Desai, M.B.B.S. Author disclosures are in the abstract and manuscript. This study did not receive outside funding.

Cannabis use disorder linked to serious heart rhythm abnormalities (Poster Presentation Mo2053)

People diagnosed with cannabis use disorder had a 50% greater risk of being hospitalized for an arrhythmia, a disorder of the heart’s rhythm, compared to non-users. Cannabis use disorder is characterized by frequent, compulsive use of marijuana, similar to alcoholism.

In this study, young African American men with the disorder, between 15 to 24 years of age, had the greatest risk of being hospitalized for arrhythmia, although cannabis use disorder was more common among white men, 45 to 54 years of age.

While some arrhythmias are benign, others can be life-threatening. “The effects of using cannabis are seen within 15 minutes and last for around three hours. At lower doses, it is linked to a rapid heartbeat. At higher doses, it is linked to a too-slow heartbeat,” said Rikinkumar S. Patel, M.D., M.P.H., resident physician in the department of psychiatry at the Griffin Memorial Hospital in Norman, Oklahoma.

“The risk of cannabis use linked to arrhythmia in young people is a major concern, and physicians should ask patients hospitalized with arrhythmias about their use of cannabis and other substances because they could be triggering their arrhythmias,” said Patel.

“As medical and recreational cannabis is legalized in many states, it is important to know the difference between therapeutic cannabis dosing for medical purposes and the consequences of cannabis abuse. We urgently need additional research to understand these issues,” said Patel. 18

Data for this study was derived from the Agency for Healthcare Research and Quality’s Nationwide Inpatient Sample (post-legalization period, 2010-2014), and this is the first, large-scale, population-based study to evaluate a link between cannabis use disorder and hospitalization for arrhythmias. Although it does not prove cause and effect, it establishes an important trend.

Co-author is Sowmya Madireddy, M.D. Author disclosures are in the abstract. This study did not receive any external funding.

Additional Resources:

Statements and conclusions of study authors presented at American Heart Association scientific meetings are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. The Association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and device corporations and health insurance providers are available at

The American Heart Association’s Scientific Sessions is a premier global exchange of the latest advances in cardiovascular science for researchers and clinicians. Scientific Sessions 2019 is November 16-18 at the Pennsylvania Convention Center in Philadelphia. More than 12,000 leading physicians, scientists, cardiologists and allied health care professionals from around the world convene at the Scientific Sessions to participate in basic, clinical and population science presentations, discussions and curricula that can shape the future of cardiovascular science and medicine, including prevention and quality improvement. During the three-day meeting, attendees receive exclusive access to over 4,100 original research presentations and can earn Continuing Medical Education (CME), Continuing Education (CE) or Maintenance of Certification (MOC) credits for educational sessions. Engage in the Scientific Sessions conversation on social media via #AHA19.

About the American Heart Association

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Research Highlights: Young people who reported using cannabis frequently had higher risk of having a stroke, according to a Virginia study. The risk of being hospitalized for arrhythmia was significantly greater among people diagnosed with…

Marijuana and your heart

Legalized marijuana is now a reality in Canada. This opening up of legal access will have a variety of health implications. In addition, marijuana is increasingly prescribed for much of what ails us, from the pain and inflammation of osteoarthritis to a host of other conditions, many of which affect seniors – the same people who are at greatest risk of heart disease. What the legal use of marijuana could mean for your heart, whether you’ve already had a cardiac event or are at risk of having one, is in many ways an open question.

Physician and researcher Andrew Pipe, MD, and behavioural scientist Robert Reid, PhD, both of the Ottawa Heart Institute’s Division of Prevention and Rehabilitation, are widely published experts in the prevention of heart disease. As Dr. Pipe put it, “When we consider marijuana and issues relating to the heart we really are steering into terra incognita.”

The long-standing illegal status of marijuana has made it a lower priority for health researchers and posed a hurdle to conducting studies. What we do know about the drug’s effects on the cardiovascular system is not a lot, said both men.

“We’ll see an increased interest in research as a result of the liberalized approach to marijuana,” added Dr. Reid, Deputy Chief of the Division.

Watch Dr. Andrew Pipe discuss marijuana and the heart with CTV Ottawa Morning Live’s Henry Burris.

What the Research Tells Us

A 2014 review article in the New England Journal of Medicine summarized what is known about the effects of marijuana on all aspects of health. The authors found that marijuana use has been associated with vascular conditions that increase the risk of heart attack and stroke, although the mechanisms by which that happens aren’t clear. The article also noted that the risk is mainly associated with immediate use of marijuana and isn’t necessarily cumulative.

Physician and researcher Andrew Pipe, MD

There is some epidemiological evidence that marijuana use in young men, in particular, is associated with an increased risk of heart attack within an hour of use, said Dr. Reid, whereas the risk in young women is not increased to the same degree.

Another article, from 2013 in the American Heart Journal, found that habitual marijuana use before a heart attack was associated with a higher mortality rate over the next 18 years, although the difference wasn’t statistically significant.

Both Drs. Pipe and Reid expect increased interest in research around marijuana use. They also both said that, based on what evidence there is, as well as common sense, trying this newly legal drug should be approached with caution and that, if you must, then don’t smoke it.

Physiological Effects of Smoking Marijuana

When you smoke marijuana, your heart rate and blood pressure increase. At the same time, smoking in general, whether tobacco, marijuana or a mixture of the two, reduces the capacity of the blood to deliver oxygen throughout the body – an effect of the products of combustion such as carbon monoxide. This combination adds up to increased risk for a cardiac event like a heart attack, particularly while a person is smoking and immediately afterward.

“There is a strong case for saying no one should ever smoke marijuana because of the products of combustion,” said Dr. Pipe. “We can say with absolute certainty that smoking marijuana will harm the ability to deliver oxygen, and that’s not good.”

While Dr. Reid pointed out that the relationship between marijuana use and heart disease remains, at this point, “largely theoretical,” there is existing evidence that marijuana use may lead to quicker onset of exercise-induced angina during a stress test among people with heart disease. This suggests another reason why it is not a good idea to use marijuana, he noted. He also noted that marijuana use could be problematic for people with an irregular heartbeat, or arrhythmia, because it activates the sympathetic nervous system.

What Happens to Your Heart When You Use Marijuana?
  • Your heart rate and blood pressure increase, forcing your heart to work harder.
  • If you smoke the marijuana, the capacity of your blood to transport oxygen throughout your body, including to your heart, is reduced.
  • The result is strain on your heart and a reduced ability to handle increased demands.

The Problem with Assessing Impact

In theory, it shouldn’t be that difficult to assess the impact of marijuana use. In reality, though, it’s actually difficult to untangle.

For one thing, marijuana is rarely used in isolation. Generally, tobacco, alcohol or both are involved. And while the amount smoked is less with marijuana, experience has shown that smoking marijuana can make it harder to quit smoking tobacco. In reality, most people use the two together, thus, as Dr. Reid punned, “clouding the issue.”

Behavioural scientist Robert Reid, PhD

“Significant numbers of individuals who smoke lots of marijuana daily come to us because they want to stop smoking,” said Dr. Pipe. “But for heavy marijuana smokers mixing it with tobacco, the likelihood of quitting is much less.”

Another problem relates to dose control. There are no standards for the production of marijuana and the amount of THC (the ingredient that gives marijuana its “high”) it contains. The problem becomes more acute when marijuana is eaten, said Dr. Pipe. People who eat marijuana may not feel the effect as quickly as those who smoke it, leading them to use more.

Marijuana and Depression

One concern frequently raised is the link between marijuana and depression. Depression is a known risk factor for heart disease, in part because it interferes with a patient’s ability to adopt healthier behaviours, and many believe that marijuana use can lead to depression.

But it’s a chicken-and-egg kind of argument. We really don’t know whether marijuana causes depression, said Dr. Pipe, or whether people who are depressed use marijuana at least in part as an effort to self-medicate. Either way, it underscores yet another area where more research is needed.

Edible Marijuana

Eating marijuana is an option to avoid the toxins associated with smoking it, but other risks are likely similar.

“Edible forms would be different in terms of impacts on the oxygen carrying capacity of blood,” said Dr. Reid, “But there would still be some [effects] in terms of heart rate and blood pressure.”

This is also a rich area for future research, said Dr. Pipe, particularly isolating and purifying the chemical compounds in marijuana that have a therapeutic effect while eliminating the psychoactive ingredients.

“We don’t advise people in pain to chew willow bark [the source of the active ingredient in Aspirin], we tell them to take Aspirin,” he said. “There’s no reason marijuana should be any different.”

What’s a Patient to Do?

With all this uncertainty, it’s hard to know the wisest course for a patient. Dr. Reid advised that patients “start asking” their care providers about using marijuana just as they would about alcohol and to use caution, until something more definitive is known.

“[Smoking marijuana] probably wouldn’t be a good idea for someone with ischemic heart disease,” said Dr. Reid, because of the reduced oxygen transport through the body. “There’s no reason to begin marijuana use, and there could be more risk associated with it.”

“Don’t smoke it!” added Dr. Pipe. “Have a careful, considered conversation with the physician who is responsible for your care.”

“I’m pretty confident saying if you don’t use it now, there’s no reason to start,” concluded Dr. Reid.

A previous version of this article was originally published in July 2017.

Cardiovascular experts weigh in on what we do and, in many cases, don’t know ]]>