Fraser Horton
Fraser Horton
Last Updated on July 10, 2021

Marijuana has been used as a medicine for thousands of years, save for the one century when it was illegal which, of course, made accessing weed difficult. In the present day, however, the healing properties of the cannabis plant are being recognized once again and the result of this is the legalization of marijuana across most states in the US as well as some other countries in the world. 

Nowadays, there are legal dispensaries where cannabis users can freely buy marijuana products either for recreational purposes or for the treatment of numerous medical conditions. A lot of individuals find cannabis more tolerable than conventional treatments, and therefore, more effective.

However, marijuana is also known to cause some side effects depending on the strain and the person’s tolerance, including an increased heart rate. 

In this article, we’ll talk about the effects of marijuana on heart rate and how it influences the cardiovascular system.

The Health Effects of Marijuana

Marijuana has a unique way of interacting with the human body via the endocannabinoid system and its cannabinoid receptors. The two main cannabinoids, THC (tetrahydrocannabinol) and CBD (cannabidiol), interact with the receptors and cause a variety of effects in the brain and the body. 

THC is the psychoactive ingredient that causes the euphoric feeling associated with marijuana, while CBD is non-psychoactive and has healing properties.

Cannabis is known to help treat the symptoms of anxiety and depression, as well as epilepsy and insomnia. It’s also used for conditions that cause chronic pain, muscle spasms, and inflammation.

Side Effects

Cannabis can also cause some side effects which are usually attributed to THC because of the way it interacts with the cannabinoid receptors. CBD is known to be more easily tolerated and it can even tone down the effects of THC.

That being said, THC is more likely to cause an increased heart rate, anxiety, paranoia, dry mouth, and dizziness. 

When THC interacts with the cannabinoid receptors in certain parts of the brain, it stimulates the sympathetic nervous system, which activates the fight-or-flight response. Subsequently, the heart starts beating irregularly and the blood flow in the muscles is increased while the blood flow to the skin is decreased.

How Much Can Marijuana Increase a Person’s Heart Rate?

Cannabis is a vasodilator, meaning that it expands the blood vessels, which subsequently produces a number of temporary changes in the body. 

Upon inhaling marijuana smoke, the heart rate temporarily speeds up and with that, the blood pressure rises. While a healthy person’s average heart rate should be between 60 to 100 beats per minute at rest, a few minutes upon marijuana consumption, the heart rate can increase by 20 to 50 beats per minute (or sometimes even double).

After about 10-15 minutes, the blood vessels start dilating, causing the heart rate and blood pressure to start lowering. This causes a rush of blood flow through the entire body, which is most pronounced in the eye area because it’s sensitive to the changes in the size of the blood vessels. This effect is what causes the well-known bloodshot eyes, commonly associated with cannabis use.

Finally, as the blood pressure lowers, the body tries to compensate by making the heart pump blood faster. It’s been estimated that the heart works about 30% harder under the influence of THC. It’s also thought that this effect is highly dose-dependent and that lower doses of THC don’t necessarily have the same effects.

CBD Has Better Effects on Cardiovascular Health Compared to THC

CBD, the other major cannabinoid, is much better tolerated than THC. It’s the most commonly used form of medical marijuana because it has anti-inflammatory, pain relief, and calming properties.

CBD can slow the heart rate and relax the blood vessels, and some research even suggests that CBD can potentially lower blood pressure, all of which is good for heart health. Additionally, it can control the potent effects of THC and balance its intensity.

Is Marijuana Safe for People With Cardiovascular Diseases?

Even though the research on the cardiovascular effects of cannabis is limited, what we do know so far suggests that people who suffer from cardiovascular diseases such as high blood pressure or heart disease, should avoid using marijuana, or choose strains that are high in CBD and low in THC.

For people suffering from heart disease, the cardiovascular events that come with smoking marijuana, such as elevated heart rate and blood pressure, may put them at an increased risk of a heart attack. In these cases, the capacity of blood to carry oxygen through the body is also reduced, which may cause dizziness when standing up.

According to the National Institute on Drug Abuse, during the first hour after inhaling marijuana an average person’s risk of getting a heart attack is five times higher than normal. After the first hour, the risk seems to rapidly decrease.

However, it’s believed that with repeated exposure to cannabis, the body can build resilience and tolerance to some of these cardiovascular events caused by THC. This is one of the things that need to be examined more closely, especially with the increased use of medical marijuana by people who are vulnerable to cardiovascular changes related to age as a risk factor.

As always, it’s highly advised to seek medical advice prior to the use of medical marijuana if you’re suffering from any kind of cardiovascular condition.

Final Thoughts – Even Though Research Is Limited, It’s Best to Avoid Marijuana Use If You Have a Heart Problem

The use of marijuana for both recreational and medical purposes has largely increased following its legalization in some states and countries. Its medical benefits are finally being recognized, but so are the side effects. We now know more about its positive and negative effects compared to the past, but there is still a lot to discover, including who should avoid or limit their marijuana use.

Marijuana, or THC in particular, has been shown to temporarily increase the heart rate, which leads to an increased risk of a heart attack in the first hours after consumption. This could be potentially dangerous for people who suffer from heart problems. Even though the risk rapidly diminished after the first hour, it’s best to avoid marijuana consumption until there is more research on the subject.

Additional Sources

Pacher, P., Bátkai, S., & Kunos, G. (2005). Cardiovascular pharmacology of cannabinoids. Handbook of experimental pharmacology, (168), 599–625. https://doi.org/10.1007/3-540-26573-2_20

Stanley, C. P., Hind, W. H., & O’Sullivan, S. E. (2013). Is the cardiovascular system a therapeutic target for cannabidiol?. British journal of clinical pharmacology, 75(2), 313–322. https://doi.org/10.1111/j.1365-2125.2012.04351.x

Subramaniam, V. N., Menezes, A. R., DeSchutter, A., & Lavie, C. J. (2019). The Cardiovascular Effects of Marijuana: Are the Potential Adverse Effects Worth the High?. Missouri medicine, 116(2), 146–153

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