Photo of a woman doing yoga by a lake
Yogic breathing exercises and asanas are a valuable way to treat stress, anxiety and depression [Image: Andrey - Wikimedia Commons]

Science gets a handle on how yoga works

19 July, 2012

Natural Health News — New evidence on the way yoga affects the nervous system could open the doors to effective treatment for stress-related conditions such as depression, anxiety, high blood pressure and cardiac disease.

A collaboration by researchers from Boston University School of Medicine, New York Medical College and the Columbia College of Physicians and Surgeons, writing in the journal Medical Hypotheses

The accumulated evidence, they say, suggests that the practice of yoga reduces stress in a specific way – by reducing the allostatic load.

The term allostatic load is used to describe the physiological consequences of chronic exposure to chronic stress.

It is used to explain how frequent activation of the body’s stress response, essential for managing acute threats, can in fact damage several organs and tissues, but especially the cardiovascular system over the long run.

Calming the stress response

When we get stressed our bodies release various hormones to mitigate the effects – this is normal and healthy. But overproduction of these hormones on a regular or irregular basis can cause medical problems  such as hypertension.

If stress levels and production of these coping hormones is continually being turned ‘on’ and ‘off’, wear and tear on the body can be particularly acute.

In particular, stress can leave the parasympatheitc nervous system (PNS) – sometimes called our body’s ‘rest-digest-nest response’ – in disarray. It can also result in low levels of the neurotransmitter gamma-aminobutyric-acid (GABA).

Low GABA activity is particularly prevalent in anxiety disorders, post-traumatic stress disorder, depression, epilepsy, and chronic pain.

Practising yoga, say the researchers, helps the body by increasing PNS and GABA activity – protecting the body and leading to an improvement in symptoms.

Vagal nerve stimulation

According to the study, the positive effects of yoga are linked to the way this ancient practice promotes vagal verve stimulation (VNS).

The vagus nerve runs from deep in the brain down to the gut and helps to regulate the heart beat, control muscle movement, breathing and digestion as well as transmitting a variety of chemicals through the body.

Stimulating the vagus nerve has a knock on effect of stimulating the PNS, which can lower heart rate and blood pressure, decrease both seizure frequency and the symptoms of depression and counteract the body’s stress response.

Yogic breathing techniques and asanas (yoga poses) fold, twist and extend the torso, stimulate the vagus nerve in multiple ways and can be effective on their own or practised in conjunction with other treatments.

“Western and Eastern medicine complement one another. Yoga is known to improve stress-related nervous system imbalances,” said Chris Streeter, MD, associate professor of psychiatry at BUSM and Boston Medical Center, who is the study’s lead author. Streeter believes that “This paper provides a theory, based on neurophysiology and neuroanatomy, to understand how yoga helps patients feel better by relieving symptoms in many common disorders.”