How Does Marijuana Affect Your Blood Pressure?

What does the research say?


In November 2017, the American College of Cardiology and the American Heart Association changed the national blood pressure guidelines. Both bodies agreed that Americans with a blood pressure of 130/80 should be treated; a move down from the long-standing 140/90 figure.

This move drastically altered the number of Americans classified as having ‘high blood pressure’, increasing from 75 million to approximately 103 million! This figure equates to around 46% of all adults! Also known as hypertension, high blood pressure is the second biggest cause of preventable heart disease and stroke deaths in the U.S., behind tobacco smoking.

Back in 2015, a government-sponsored study showed that death from a heart-related cause fell over 40%, and heart failure rates dropped 38% when a person’s systolic blood pressure was below 120 compared to those brought to a target below 140.

The links between hypertension and cardiovascular events are well-known; as is the strong link between cigarette smoking and heart problems. An interesting angle that hasn’t been properly explored yet is the effect of cannabis on blood pressure. In this article, we check out high and low blood pressure and determine if there is any connection to the rise and fall of it when a person uses marijuana.

What is High Blood Pressure?

Before we go any further into the effects that marijuana has on blood pressure, we need to understand the difference between normal blood pressure and high blood pressure. As your heart beats, it’s pumping blood through the arteries; to determine blood pressure, we measure the force of blood that is pressing against the artery walls. Systolic pressure is used to measure the force of the blood in your arteries when the heart pumps. The force that is measured at the moment of rest between the heartbeats is diastolic pressure.

High blood pressure essentially means that the heart has to work harder to pump blood, and this causes weakening and strain. In addition, it causes the artery walls to get damaged over time. Generally, normal blood pressure for healthy adults should be less than 80 millimeters diastolic, and less than 120 millimeters systolic.

High blood pressure has been deemed as the “silent killer” because often it doesn’t have any symptoms, and is only discovered at times of a medical checkup. When symptoms do occur, it’s usually only when the high blood pressure has increased to life-threatening levels. Hypertension shouldn’t be ignored as it can cause some serious health problems if it’s left untreated.

High blood pressure increases the individual’s risk of heart attack, cardiovascular disease, and stroke. Obesity, stress, poor diet, tobacco, physical inactivity, and alcohol use are all factors which can cause an increased possibility of developing high blood pressure.

Marijuana and High Blood Pressure

It is an increasingly common condition where the long-term force of the blood against your artery walls becomes so high that it could ultimately cause cardiovascular conditions such as heart disease. Your blood pressure is determined by the amount of blood pumped by the heart, and the level of resistance to blood flow in your arteries. The narrower your arteries and the greater the rate of blood pumped by the heart, the higher your blood pressure.

It is entirely possible to have hypertension for years without any symptoms. However, in the background, your blood vessels and heart continue to get damaged, and eventually, you could endure a serious cardiac episode such as a stroke or heart attack. High blood pressure usually develops over a few years, but it easily uncovered if you have a regular physical examination.

There are cases where your blood pressure could reach a dangerously high level with no symptoms attached. However, signs of high blood pressure could include nosebleeds, shortness of breath, and headaches. Ideally, you will have a blood pressure reading every two years once you turn 18, and annually once you turn 40. However, individuals younger than 40 at high risk should undergo an annual reading.

High blood pressure is divided into two types:

Primary Hypertension

This type of blood pressure builds up over a few years and carries no symptoms.

Secondary Hypertension

This is high blood pressure caused by an underlying condition. It often appears suddenly and causes even higher blood pressure than primary hypertension. Here are a few conditions and medications that can cause it:

  • Thyroid Problems
  • Kidney Issues
  • Obstructive Sleep Apnea
  • Congenital Birth Defects
  • Drugs such as amphetamines and cocaine
  • OTC painkillers, cold remedies, birth control pills, and some prescription drugs.

Risk Factors

There is a wide range of risk factors, including:

  • Age: You are more likely to have hypertension as you get older. Men are more at risk until age 64; women are more likely to have high blood pressure aged 65+.
  • Family History: Hypertension can run in the family.
  • Ethnicity: Individuals of African heritage are at greater risk than whites, and can develop it at a younger age.
  • Weight: You have a greater likelihood of hypertension if you are overweight or obese.
  • Lifestyle: Inactive People tend to have a higher resting heart rate. As such, their hearts must work harder, and it places a greater force on the arteries. Eating too much salt, too little potassium, and consuming alcohol & tobacco, all increase the risk of hypertension.

High blood pressure can lead to conditions such as heart failure, thickening blood vessels in the eye, metabolic syndrome, aneurysm, stroke or heart attack, and trouble with your memory.

How is Blood Pressure Measured?

Your physician will put an inflatable arm cuff around the arm and use a pressure-measuring gauge to take your blood pressure. You will notice that the reading has two numbers, and is given in millimeters of mercury (mm Hg). The first number measures the pressure in the arteries when your heart beats and is known as systolic pressure. The second number measures the pressure in the arteries between the heart’s beats and is called diastolic pressure.

Your blood pressure is considered normal if the systolic pressure figure is below 120 and the diastolic figure is below 80. A healthy reading would be 117/78 mm/Hg, for example. Here are a few other classifications based on blood pressure readings:

  • Elevated Blood Pressure: This is when your systolic figure is between 120 and 129, and your diastolic figure is below 80.
  • Stage 1 Hypertension: You are in this category if your systolic figure is 130-139, and your diastolic figure is 80-89. Until the change in November 2017, individuals in this range were not classified as having hypertension.
  • Stage 2 Hypertension: At this point, you are firmly in the danger zone as your systolic figure is 140+, and your diastolic figure is 90+.

What About Low Blood Pressure?

Also known as ‘hypotension,’ low blood pressure is when your systolic figure is below 90, and the diastolic figure is below 60. You may think it is a desirable condition, but it is usually accompanied by symptoms such as fatigue, blurred vision, fainting, dizziness, and a loss of concentration.

In extreme cases, the symptoms become worse and include a weak and rapid pulse, rapid, shallow breathing, and cold, clammy, pale skin. A sudden fall in blood pressure is potentially dangerous. For example, a drop in systolic pressure from 115 to 95 may cause dizziness and fainting because the brain doesn’t receive enough blood. Conditions and medications that can cause hypotension include:

  • Dehydration
  • Heart problems such as heart valve issues
  • Pregnancy
  • Severe infection
  • Severe allergic reaction
  • Lack of nutrients such as Vitamin B12
  • Blood loss
  • Alpha-blockers such as prazosin
  • Antidepressants such as doxepin
  • Beta-blockers
  • Water pills

Seniors are at greater risk of a sudden fall in blood pressure after a meal or when they stand. Diabetes, Parkinson’s, and certain heart conditions all increase the risk.

How Marijuana Affects High Blood Pressure

There are studies which claim weed increases blood pressure and others which suggest it reduces it! Scientists are now convinced that if you have heart disease and are under stress, you will develop chest pain more rapidly if you smoke marijuana. This reaction is due to the effects of cannabinoids on the cardiovascular system, including dilation of blood vessels, increasing resting heart rate, and causing the heart to pump even faster.

Interestingly, for individuals in this situation, the risk of heart attack is several times higher in the first hour after using weed than normal. While this doesn’t prove weed is harmful to the heart of healthy individuals, it is a warning sign for anyone with a history of heart disease.

Back in 2017, a study by Yankey et al. was published in the European Journal of Preventive Cardiology. It involved asking over 1,200 participants whether they used weed. According to the research, conducted in 2005-2006, cannabis users were 3.42 times more likely to die from hypertension, with the risk increasing by 4% with each year of use.

However, in 2019, the study was RETRACTED with the agreement of the authors! The reason was a methodological error which resulted in ‘immortality bias’ within the study’s findings.

A study by Alshaarawy and Elbaz looked at marijuana use and blood pressure levels from 2005-2012. The research, published in the Journal of Hypertension in August 2016, involved analyzing 12,000 volunteers over seven years. Overall, those who used weed within the previous 30 days had a slightly higher systolic pressure reading than non-users.

Marijuana and Low Blood Pressure

To confuse matters, there is research which suggests marijuana users experience a slight increase in blood pressure immediately after use, only for their blood pressure to drop within minutes; a process that leaves them feeling groggy and sleepy. After a few weeks of moderate to regular use, you will probably develop a ‘tolerance’ which can have a significant effect on how weed impacts your blood pressure.

A review by Sidney, published in the Journal of Clinical Pharmacology in November 2002, looked at the cardiovascular consequences of cannabis use. In the research paper, Sidney says that once a person has developed a tolerance to marijuana, their heart rate and blood pressure fall immediately after consumption.

In February 2008, a study by Pacher, Batkai, and Kunos, was published in the Handbook of Experimental Pharmacology. It wrote that the endogenous cannabinoid system was implicated in the mechanism of hypotension! It also said that cannabinoids had been considered as potential antihypertensive agents. In other words, cannabinoids such as THC could be used to keep blood pressure levels under control.

Does Marijuana Increase the Risk of Heart Attack or Stroke?

Opponents of cannabis have tried to claim that the herb increases the risk of a heart attack or stroke. Remember the Harvard study, which claimed the risk of having a heart attack rose by 400% in the first hour after use? Anti-marijuana advocates often use it as proof that the herb is dangerous.

They either fail to realize, or else they don’t care, that the study, which was published almost 20 years ago, looked at a study of almost 3,900 people who had survived heart attacks. In other words, your chances of a heart attack increase in the first 60 minutes after smoking weed if you have already had a heart attack! The increased risk could be down to combustion and exposure to certain chemicals, a similar danger with tobacco cigarettes.

Back in the real world, few studies have ever found a serious link between marijuana and an increased risk of a heart attack or stroke, and quite a few have discovered the opposite. A 2006 study by Rodondi et al. published in The American Journal of Cardiology, looked at over 3,600 black and Caucasian volunteers to see if there was any link between weed and cardiovascular risk factors. They found no long-term causal link.

A study by Tompkins et al. presented at Heart Rhythm 2018, looked at one million patients to assess the arrhythmic effects of marijuana after a heart attack. It found that smoking weed was unlikely to be associated with an increased risk of ventricular tachycardia and ventricular fibrillation. Interestingly, the researchers also discovered that weed users had a lower risk of atrial fibrillation and in-hospital mortality.

Final Thoughts: Does Smoking Marijuana Increase Blood Pressure?

It is often assumed that smoking weed causes high blood pressure because of the links between smoking tobacco cigarettes and hypertension. However, research into the effect of cannabis on blood pressure, albeit limited, shows that the herb can cause an initial spike in blood pressure, followed by a drop amongst experienced users who have developed a tolerance.

If you have a tolerance for marijuana, you may not even experience the initial rise in blood pressure. The often-cited Yankey study, which was supposed to provide clear evidence that cannabis causes an increase in blood pressure, was recently retracted. There were flaws in the methodology and so the study is no longer available for public view.

One of the largest studies to date involved more than 12,000 people over seven years and was only able to show a slight increase in systolic blood pressure amongst marijuana users when compared to non-users. There is also research which suggests that using the herb can help control a person’s blood pressure.

Unfortunately, there isn’t enough research material available to draw a definitive conclusion. From what we know so far, it isn’t a good idea to smoke cannabis if you have already suffered from a heart-related issue; much like it is a poor choice to use cigarettes. Certainly, high blood pressure is more likely to be caused by a bad diet and unhealthy lifestyle than through the occasional use of marijuana.

Nonetheless, we don’t recommend using weed specifically to lower your heart rate. Speak to your doctor before considering medical marijuana for any condition.

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