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Can Smoking Marijuana Elevate the Risk of a Heart Attack?

— August 29, 2019

While offering many proven benefits, there are also some risks associated with marijuana use. This is particularly true for those with cardiovascular issues.

Most Americans overwhelmingly support the legalization of marijuana for both medical and recreational use. According to 2018 data from a general social survey by Pew Research Center, 62% of Americans opine that marijuana should be legal.

Concerning actual consumption, the 2017 National Survey on Drug Use and Health show that 15% of U.S. citizens of 18+ years old are current users.

Graph courtesy of
Graph courtesy of

Now, while there’s overwhelming evidence on the benefits of marijuana, experts say that heart racing after smoking marijuana isn’t good at all. 

The American Heart Association says that cannabis use elevates the risk of acute cardiovascular events including heart attacks, stroke, and heart rhythm disorders. And an increased heart rate is one of the telltales. 

Case study: Marijuana lollipop-induced myocardial infarction (heart attack)

The Canadian Journal of Cardiology records the case of a 70-year old man who was rushed to the hospital with severe chest pain, diaphoresis (excessive sweating), and pallor (unhealthy paleness).

The man – with known stable coronary heart disease – had consumed a lollipop infused with 90mg of THC to manage pains and improve sleep. On the contrary, crushing chest pains began 30 minutes later accompanied by worsening functional status.

Could there have been a link between marijuana and these tragic events?

Doctors examining this case concluded that marijuana was the major cause for these occurrences. Precisely, they note that the man was exposed to way much THC in the 90-mg dose that was in the lollipop.

But it’s a well-known fact that it’s almost impossible to overdose on marijuana. So, how can this be explained?

Well, to understand this link, we’d need to unpack the impact of marijuana on cannabinoid receptors 1 and 2 (CB1 and CB2) and how these can trigger a heart attack.

CB1 Receptors and their Impact on Heart Rate and Heart Attacks

Cannabinoid receptors are key players in the endocannabinoid system. This is a complex system found all over the body and responsible for regulating various physiological and cognitive processes such as mood, memory, pregnancy, fertility, and pain sensation.

The endocannabinoid system works by sending chemical messages to receptors mainly CB1 and CB2 subtypes.

While CB1 receptors are mainly expressed in the brain, they are also found all around the body including in the cardiovascular system: heart muscle and blood vessels.

When you consume cannabis, hundreds of cannabinoids are released into your blood system including THC and CBD.

THC (the key active ingredient that causes the HIGH) binds to both CB1 and CB2 receptors in the endocannabinoid system but more-so to the CB1 receptors. This is enough reason to believe that too much THC in the blood could impact the cardiovascular system and trigger a heart attack.

Here are the possible impacts of THC:

Lowered Blood Pressure and increased Heart Rate

When THC enters the blood system, it causes vasodilation (widening of blood vessels) thereby leading to decreased blood pressure.

As a result, the heart has to work harder to pump more blood. This is what causes an elevated heart rate a few minutes after lighting a joint. 

The heart normally makes 70 to 80 beats per minute. However, after inhaling marijuana smoke, this rate increases by anywhere between 20 and 50 minutes per minute. It could even double depending on the amount of THC ingested, according to the National Institute on Drug Abuse.

This elevated heart rate could persist for up to three hours and it has been found to increase the risk of heart attacks by up to four fold.

Increased risk of atherosclerosis

Atherosclerosis is an inflammatory disease of the arteries that is caused by the build-up of cholesterol, fats, and other materials on their inner walls. These deposits are also called cholesterol plaque.

Atherosclerosis is a progressive and painless process that eventually causes blocked arteries thereby inhibiting the flow of blood – a major contributor to cardiovascular diseases and events such as heart attack and stroke.

How does marijuana increase the risk of atherosclerosis?

When CB1 receptors are overactivated, they promote the increase of harmful chemicals known as reactive oxygen species.

These are free radicals that contain oxygen and that react with other chemicals in the cells of the artery walls. The buildup of reactive oxygen cells damages DNA, RNA, and proteins eventually leading to cell death.

In response to this risk, a meta-analysis study published in the National Institutes of Health shows that the CB2 receptors cause an immune system response that involves the infiltration and activation of special white blood cells known as a monocyte/macrophage.

While these cells usually work to make things better, they become part of the plaque and end up being deposited on the arterial walls leading to inflammation.

Also, overactivation of CB1 receptors elevates the amount of oxidized bad cholesterol (LDL). The oxidized LDL further activates macrophages thereby increasing the accumulation on the walls.

Marijuana causes exercise-induced angina

Angina is a chest pain (or burn) characterized by a feeling of pressure or squeezing in the chest. While it isn’t a heart attack, it is often a warning sign and a symptom of life-threatening heart disease.

Angina occurs when there’s a blockage in the arteries that take oxygen-rich blood to the heart. Physical activity and stress are the most common causes of this heart condition.

However, there is evidence that marijuana use can cause it too. This is why most experts advise individuals with heart issues to exercise great caution when toking.

High THC levels activate the Sympathetic Nervous System

At high levels, THC is known to cause anxiety and hallucinations. These conditions are demonstrated by the release of catecholamine (stress hormone), an elevated heart rate, and high blood pressure.

In the event of these stressors, the body naturally triggers compensatory responses including activating the Sympathetic Nervous System (SNS). The role of the SNS is to provide inotropic support by modifying the rate and force at which the heart muscles contract.

Unfortunately, although the SNS is triggered to rescue the failing heart, it eventually adds to the problem itself thereby putting the individual to an even higher risk of a heart attack. This is yet another reason why you want to be careful with marijuana especially if you have an irregular heartbeat or any other existing cardiovascular condition.

Final Word

While marijuana is associated with loads of health benefits, experts advise being careful with how much you consume.

If you have existing heart problems or you are predisposed to developing one, you might want to avoid THC altogether and instead go for CBD which is non-psychoactive.

It’s also important that you consider your tolerance. People with higher tolerance levels are likely to experience fewer side effects compared to those with lower tolerance levels.

Lastly, in case you experience signs such as shortness of breath and sharp chest pains after lighting a joint or eating a brownie, take one full-sized aspirin (or four baby size pills) and seek medical care immediately.

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