Yoga as a Moderator on the Effects of Stress on Hypertension

Kavya Vaidyanathan

University of Michigan


With two million new cases being diagnosed each year, hypertension is a challenge to the medical profession and a common problem facing many Americans today. Current conventional treatments for treating hypertension decrease peripheral resistance, blood volume, or the strength and rate of myocardial contraction. Some patients are resorting to alternative medicine either as a supplement or substitute. Prior research has found a variety of alternative therapies to be successful in reducing high blood pressure, including diet, exercise, stress management, supplements, and herbs. Stress is one of the factors that cause secondary hypertension. In this research study, yoga is explored as a stress reducing activity, thus moderating the effects of stress on hypertension.


High blood pressure affects twenty five percent of American adults1. There has recently been an increasing awareness of the effectiveness of alternative medicine, which explores the extent of the connection between the mind and body, part of which is a result of influences from Asia where practices of acupuncture and natural healing are preferred to medications. Yoga has grown quickly in popularity in the United States as well as in many other Western nations. High blood pressure is a condition that has an incredibly high mortality rate in this country. 31.6 percent of Americans with hypertension do not know that they have it2.

High blood pressure describes the high force of blood against artery walls. It means that the heart is working much harder than the heart of a normal healthy human. Hypertension is a dangerous condition that does not have a cure, but it can be kept in check by taking medications regularly and by eating healthy meals

Yoga, a practice of controlling the mind and body, is an ancient art that began in India over thousands of years ago. Because it involves breath control, meditation, and physical postures, it is supposed to increase the vitality of the human body, help with concentration, calm the mind, and improve common physical ailments (Lamb, 2004).

While there is relatively little information that directly links yoga with high blood pressure, there is a common factor that the two subjects share- stress. Numerous references and sources discuss a relationship between hypertension and stress as well as a relationship between relaxation techniques and stress. In the next sections, this paper will explore the question of whether there is a definite correlation between yoga and hypertension, and, if so, whether there is a causal relationship present, where a regular practice of yoga would have a positive effect on lowering high blood pressure.


Stress is experienced when "emotional, physical, or environmental demands challenge or exceed a person's personal resources and ability to cope effectively" (Sheps, 2002). There are two types of stress, namely acute stress and chronic stress. Acute stress is transitory, while chronic stress occurs for a prolonged period of time (Hendrickson, 2004).

The stress response, also called the general adaptation syndrome (or the "fight-or-flight" response), relates to acute stress and is a "physiological reaction that rallies you to action when you encounter a perceived threat" (Sheps, 2002). There are three stages of the stress response. First, there is the alarm reaction, which occurs when you are alert and on your guard and when your arteries constrict and heart rate speeds up. During this stage, you feel threatened by someone or something, and the muscles tense and respiration increases. When you are ready to fight the challenge, the resistance reaction kicks in, and during this stage the respiration rate, blood pressure rate, and temperature remain high. Once the threat is past, the rush of stress hormones subsides, and blood pressure, pulse, and respiration rates all return to their normal levels (Myers, 2001).

However, in chronic stress, where stress is continuous, hormone levels remain elevated, and the body permanently keeps the ready state (Whitaker, 2000); during chronic stress, the body is constantly feeling stressed or threatened, and so the resistance state remains. The muscles remain tense, the pulse rate remains high, and the blood pressure increases. The last stage, known as the exhaustion stage, occurs when the adrenal hormone stores are depleted and organ systems begin to fail (Sheps, 2002). The accumulation of stress contributes to the onset of many diseases and conditions. One of those conditions is high blood pressure or hypertension.


High blood pressure is the most common chronic illness in the United States (Sheps, 2002). It is a condition that is common among people over the age of 35. According to Dr. Suresh Ramasubban, a pulmonary physician at Rush Hospital in Chicago, blood pressure is largely the result of two main forces. The first force, called the stroke volume, is the force created as the blood is pumped into the arteries. The second force is created as the arteries resist the blood flow. Hypertension is a type of cardiovascular disease characterized by elevation of blood pressure above the level considered normal for people of similar racial and environmental backgrounds. Because it affects the entire circulatory system, hypertension can be detrimental to all the major organs, including the heart, brain, and kidneys. It may contribute to death from heart failure, heart attacks, stroke, and even kidney failure.
Hypertension is defined as "an abnormal condition in which the blood pressure exceeds the accepted normal reading of 140/90" (Fortmann & Breitrose, 1996). The first number refers to the systolic pressure, which occurs when the blood pressure is at its highest when the left ventricle of the heart contracts. The second number, the diastolic pressure, is the lowest blood pressure when the heart is at rest (Rowan, 1986).

There are two types of high blood pressure: essential and secondary. Essential high blood pressure is the more common, affecting over ninety percent of high blood pressure patients. However, it is different from secondary hypertension because it does not have an obvious cause (Sheps, 2002), making it more difficult to diagnose hypertension, since high blood pressure is usually symptom-free (Fortmann & Breitrose, 1996).

Stress and Hypertension

Many sources and studies point to a direct relationship between stress and high blood pressure. Chronic stress increases blood pressure (Whitaker, 2000). This is demonstrated by the fact that during a period of stress, the body releases the hormones epinephrine (adrenaline) and cortisol, which increase high blood pressure by narrowing the blood vessels and increasing the heart rate (Sheps, 2002). Also, prolonged stress causes resistance and exhaustion (Whitaker, 2000). In a recent study, 200 men who had worked at stressful jobs for at least 25 years were interviewed. The study showed that there was a 4.8-point rise in systolic blood pressure when the men were at work and a 7.9-point rise when the men were at home (Landsbergis, Pickering, Warren, & Schwartz, 2003).

Air traffic controllers tend to develop high blood pressure at almost six times the rate of people in lower stress jobs (McGowan & McGowan-Chopra, 2001). Cloistered nuns were much less likely to develop high blood pressure than were women of their same age living in the same geographical area but exposed to the stresses of everyday life (McGowan & McGowan-Chopra, 2001). Police officers of the Buffalo police force as a group have higher-than-average pulse rates and higher diastolic blood pressures (Baker, 2004). The research conducted so far on the effects of stress reduction seems to have a positive association with hypertension (Whitaker, 2000; Sheps, 2002; McGowan & McGowan-Chopra, 2001; Baker, 2004).

Although medicine may be the common cure to almost all ailments, there are claims of alternate therapies that control high blood pressure. One such claim is yoga and this therapy has been recently introduced to the Western world.


Yoga is an ancient art that is defined as the union of the soul with God (Anand, 2000). It is "a path of personal spiritual development that utilizes meditation to bring enlightenment, self-realization, and, ultimately, the attainment of God and bliss" (p. 109). Originally, the ultimate goal of yoga was called samadhi, or self-realization (Iyengar, 2001).

There are four types of yoga: Raj yoga, Karma yoga, Jnana yoga, and Bhakti yoga (Anand, 2000). Raj yoga, which is the yoga of meditation or concentration, is the type that is most commonly used in the West today. The Raj yoga consists of eight steps, and each step involves self-control, muscle-relaxation postures, breath control, concentration, and deep meditation. Three out of the eight steps are most common in the Western world: Pranayama, Asana, and Dhayana (Mishra, 1987). Pranayama utilizes breath control, where the breath is harnessed during inhalation and exhalation. The asanas are the different postures that help to tone the body. Dhayana consists of meditation and concentration.

The word meditate comes from the Latin word meditari, which means, "to think or reflect upon" (Bonadonna, 2003). The most popular form of meditation is called Transcendental meditation (Sorgen, 2002). It is defined as a simple mind-body technique that allows you to gain a unique state of restful awareness or alertness. Mindfulness meditation is the more difficult of the two (Bonadonna, 2003). It is defined as attempting awareness of the whole perceptual field. More than 2 million Americans have learned meditation over the past years (Bonadonna, 2003). Recent studies and evidence have demonstrated that such yoga practices are effective in reducing stress.

Stress and Yoga

There is substantial evidence that yoga and stress are directly linked. According to yoga, stress is an imbalance at the mental, physical, or emotional level. Yoga is directed at improving our ability to cope with stressors. The tension associated with stress is stored mainly in the muscles, the diaphragm, and the nervous system. If these areas are relaxed stress is reduced, minimizing the impact of stress on the individual (Iyengar, 2001). In a study involving 73 elderly men and women, some of them were asked to meditate daily (Myers, 2001). After three years, one-fourth of the nonmeditators had died, while all of the meditators were still alive (Myers, 2001). An 8-week study was conducted on medical and premedical students to see if regular meditation for the 8-week period would make the students less anxious and stressed during an examination period (Bonadonna, 2003). The results were positive, the meditation did lower the stress and anxiety level of the students (Bonadonna, 2003).

In another study led by Dr. Schneider, Dean of the College of Maharashi Vedic Medicine at the Maharashi University of Management in Iowa, transcendental meditation (TM) was compared to muscle relaxation in its effectiveness in controlling stress (Sorgen, 2002). Out of the 197 participants, the TM group had a significant reduction in blood pressure in comparison to the progressive muscle relaxation group. Another study took place at the University of Wisconsin at Madison, where brain imaging was used to show that meditation shifts the brain activity in the prefrontal cortex (which is the area of the brain directly behind the forehead) from the right hemisphere to the left (Stein, 2003). By meditating regularly, the brain is reoriented from a stressful fight-or-flight mode to one of acceptance, a shift that increases contentment (Stein, 2003).

A study conducted by the TM program measured the amount of cortisol in the body as participants of the study relaxed. The experimental group, where the participants meditated, had a significant drop in the level of cortisol during the meditation, and the cortisol level only rose slightly after the meditation was completed (Stein, 2003). On the contrary, the control group, where participants simply relaxed with their eyes closed, had only a small change in the level of cortisol both during and after the relaxation (Stein, 2003). The research conducted thus far on the effects of yoga, i.e., relaxation of muscles and mind on stress prove that yoga reduces stress (Iyengar, 2001; Myers, 2001; Bonadonna, 2003; Stein, 2003).


Supplementary treatments have been researched extensively in recent years. Lifestyle modifications, also termed as non-pharmacologic therapy, have an important and expanding role that complements drug therapy (Appel, 1999). Also, non-pharmacologic therapies can serve as initial therapy in Stage 1 hypertensive patients, facilitate medication step down or withdrawal in patients with well-controlled hypertension, and prevent hypertension in high-risk populations (Appel, 1999). Current research illustrates that yoga reduces stress (Stein, 2003; Iyengar, 20001; Bonnadona, 2003) and that by reducing stress, hypertension can be reduced (Whitaker, 2000, Landsbergis, et al., 2003; Sheps, 2002; McGowan & McGowan-Chopra, 2001). This paper proposes that yoga has a moderating effect on hypertension on stress as illustrated in Figure 1. This moderating effect can be used as a supplementary treatment to hypertension. Yoga practice unites the mind and body activities and offers stress management techniques essential in managing hypertension. However, it is impossible to conclude that there is a causal relationship. The only way to demonstrate that a continuous practice of yoga actually lowers hypertension would be to conduct a controlled study that directly tests yoga and its effect on hypertension. There is one such study being conducted at the Duke University Medical Center3. Known as the "Calm Down" study, it looks at whether practicing meditation and relaxation techniques can lower hypertension by reducing the effects of stress. This study is currently in progression and is expected to last for at least one more year.

1From CDC's High Blood Pressure Fact Sheet (http://www.cdc.gov/cvh/library/fs_bloodpressure.htm)
2From AHA statistics (http://content.nhiondemand.com/dse/consumer/HC2.asp?objID=100228&cType=hc)

3From Duke University Medical Center (http://www.dukehealth.org/clinicaltrials/20041109141616610)


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