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How Does Marijuana Affect Blood Pressure?
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Marijuana can cause a drop or rise in blood pressure, depending on how often you use it.

Have you ever felt your heart racing or pounding after smoking marijuana? If so, you’re not alone. One of the most common side effects of marijuana is an elevated heart rate, also known as tachycardia. A rise in heart rate usually causes your blood pressure to rise too.

But how marijuana affects heart rate and blood pressure depends a lot on the individual. While new users often notice a rapid heart beat after consuming marijuana, people who use marijuana regularly tend to experience the opposite effect.

Some researchers believe marijuana may even be useful for treating high blood pressure, commonly known as hypertension.

Marijuana Raises Blood Pressure in Short Term Users

If you smoke marijuana for the first time or after a long break, you’ll most likely experience a temporary spike in heart rate and blood pressure.

This effect was first documented by studies published in the 1970s, which mostly involved scientists giving marijuana to volunteers in a controlled setting and recording the effects. (5)

Compared to blood pressure, the effect that marijuana has on heart rate is more noticeable. The increase in heart rate begins almost immediately after smoking marijuana and peaks at around 30 minutes. (1)

During the peak, heart rates of 150 bpm (beats per minutes) or more have been recorded. In comparison, the average resting heart rate for most adults is between 60-100 bpm.

The increase in blood pressure caused by smoking marijuana is less substantial. Some studies have recorded a slight rise in blood pressure (1) while others have recorded no change at all. (2)

Nevertheless, as the effects of marijuana wear off, heart rate and blood pressure gradually return to normal, usually within 90 minutes of consumption.

Studies show that the impact of marijuana on heart rate and blood pressure is dose-related. (1) Larger doses of marijuana cause a more significant rise in heart rate and blood pressure than smaller doses.

Marijuana Lowers Blood Pressure in Long Term Users

What happens if you smoke marijuana frequently? Oddly enough, there’s a good chance you’ll experience a decrease in heart rate and blood pressure.

Early studies from the 1970s found that regular use of marijuana could lead to long-lasting decreases in blood pressure and heart rate. Specifically, a 1975 study found that oral doses of THC given every 4 hours over a span of 20 days lowered systolic and diastolic blood pressure in healthy volunteers. (3)

The study also confirmed that regular users of marijuana can develop a tolerance to the rapid heart rates commonly seen in novice users. In fact, by the end of the study, subjects had a slower resting heart rate than before.

Marijuana’s ability to lower blood pressure may be even greater in people with hypertension.

In a 1979 study, researchers studied the effects of marijuana in a group of volunteers with high blood pressure and normal blood pressure. (4) After smoking, the subjects with high blood pressure experienced a greater drop in blood pressure than those with normal blood pressure.

These findings have led some researchers to believe that THC may hold promise as a treatment for hypertension. (5)

See Also

Marijuana May Be Able To Treat Hypertension

After early studies showed that marijuana could lower blood pressure, researchers shifted their focus to the biological mechanisms behind the effect. (5)

The discovery of the endocannabinoid system helped researchers better understand THC’s effects on the cardiovascular system. The endocannabinoid system consists of the body’s own cannabinoids and the pathways that they activate, known as cannabinoid receptors.

As it turns out, THC mimics the effects of natural cannabinoids by binding to the same pathways found throughout the body. One of these pathways is the CB1 receptor, which is present in the cardiovascular system, specifically in tissues of the blood vessels and heart.

When activated by cannabinoids, CB1 receptors have been shown to have antihypertensive effects by causing blood vessels to dilate and weakening contractions of the heart. (5)

Most drugs prescribed for treating hypertension work in a similar way to lower blood pressure. Likewise, animal studies involving THC have shown positive effects in reducing hypertension. (6)

Unfortunately, many researchers consider the psychoactive effects of THC as a barrier to its use as a medicine.

As a result, recent studies have focused on developing synthetic cannabinoids that can target the same biological pathways as THC without causing a high. (5)

Sources
(1) https://www.ncbi.nlm.nih.gov/pubmed/4936140
(2) http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0447.1992.tb03247.x/abstract
(3) http://onlinelibrary.wiley.com/doi/10.1002/cpt1975183287/abstract
(4) https://www.ncbi.nlm.nih.gov/pubmed/468444
(5) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2228270/
(6) http://jpet.aspetjournals.org/content/321/2/663

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