The stress-reducing benefits of yoga have been purported for ages. Now scientific researchers are beginning to quantify and qualify the various ways this stress reduction can be measured.
In one study, 24 women under stress voluntarily enrolled themselves in yoga classes, two 90-minute classes per week. Women who participated for three months were compared to a waiting list group. The yoga group reported statistically significant improvements in perceived stress, anxiety, vigor, well-being, fatigue and depression. Those suffering from back pain and headaches reported significant pain relief, and salivary cortisol measurements were markedly decreased after participation.
Cortisol is a hormone released by the adrenal gland, in response to stress. It increases blood sugar levels, aids in fat and protein metabolism and decreases bone formation. It suppresses the immune system. Chronically high circulating cortisol levels have detrimental side-effects, such as sodium retention and potassium loss, an undesirable effect that can contribute to or cause high blood pressure. Cortisol counters the effects of insulin, which can lead to insulin resistance and type 2 diabetes. High cortisol levels caused by chronic stress can also contribute to osteoporosis, autoimmune diseases and even thyroid hormone imbalances.
The study concluded that “further investigation of yoga with respect to prevention and treatment of stress-related disease is warranted” especially because “emotional distress is an increasing public health problem.”1 Similar results were published in another study.2
In a study of asthmatic children practicing yoga for 20 minutes per day for 40 days, improvements were noted in lung capacities. Reductions in cortisol levels and rescue medication usage were reported.3
Constant over-activation of the sympathetic nervous system (SNS), or hypothalamic-pituitary-adrenal (HPA) axis results in the over-secretion of cortisol, epinephrine and norepinephrine, creating a chronic state of “fight or flight.” This over-stimulation of the HPA axis and SNS has also been linked to infertility, obesity, depression and substance abuse.
Numerous studies show that practicing yoga results in an immediate balancing of autonomic nervous system tone by reducing SNS activity. Yoga results in a reduction in stress levels and cortisol levels as discussed above. Catecholamines, namely norepinephrine and epinephrine levels are reduced, as is blood glucose, and plasma renin. Yoga reduces heart rate, and both systolic and diastolic blood pressure. In addition yoga counters the negative effects of stress on the immune system by raising levels of immunoglobulin A, immunoglobulin M and natural killer cells. Yoga has been shown to decrease levels of inflammatory markers in the blood stream, such as high sensitivity C-reactive protein as well as reduce inflammatory cytokines such as interleukin-6 and lymphocyte-1B.4
These studies suggest that both healthy and diseased populations can benefit significantly from yoga, and the benefits extend well beyond those obtained by the rigors of stretching alone. The integration of the mind and body through the breath, which balances the SNS and HPA axis, brings measurable chemical and hormonal harmony to our being.
- Rapid stress reduction and anxiolysis among distressed women as a consequence of a three-month intensive yoga program. Michalsen A, Grossman P, Acil A, Langhorst J, Lüdtke R, Esch T, Stefano GB, Dobos GJ. Med. Sci. Monit. 2005 Dec;11(12):CR555-561. Epub 2005 Nov 24.
- Effects of yoga on depression and anxiety of women. Javnbakht M, Hejazi Kenari R, Ghasemi M. Complement Ther Clin Pract. 2009 May;15(2):102-4. Epub 2009 Mar 20.
- Galantino ML. Therapeutic effects of yoga for children; a systematic review of the literature. Pediatr Phys Ther Spring 2008;20(1):66-80.
- Ross A, Thomas S. The health benefits of yoga and exercise: a review of comparison studies. J Altern Complement Med. 2010 Jan;16(1):3-12.