Yoga for Mental Health- a Neuroscience Perspective

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The ancient practice of yoga has expanded to all corners of today’s world. Recently it has gained popularity in the West, with the number of Americans practising yoga rising by 50%, from 22 to 35 million adults, between 2012 to 2017. While some may argue that this rapid expanse has distorted the original ‘mind, body, soul’ focus of yoga, I feel that this is does not matter. Whether your intention before you arrive on the mat is to ascend into the cosmos, or simply to tone your butt, you are still slowing down and breathing deeply. There are claims that this helps mentally and works as a kind of lifehack. Many Western yogis practice to gain physical benefits and continue because they notice subsequent mental improvements. As someone who is interested in the brain, I want to know what these mental benefits are, and what yoga can offer us in a world rife with mental health problems.

So, what is yoga? The Sanskrit word ‘Yuj’ means to unite, making yoga the union of individual consciousness with the divine consciousness. The yoga sutras text, written by Indian philosopher Pantajali, is an eight-limbed approach to a meaningful and spiritual life. One of these limbs is the ‘asana’, the physical posture, and makes up one eighth of the path to enlightenment. The control of behaviour, the breath, and the senses, is equally important. So although your hamstrings will benefit for the many downward dogs you go through in a session, unfortunately they alone you won’t provide transcendence from your ego. Your brain may gain the greatest benefit from yoga by the addition of focus on breath and coherent breathing.

To investigate how yoga affects us mentally, it is important to look at physiology. The autonomic nervous system, the body’s autopilot, is divided into two modes. These are the sympathetic ‘fight or flight’ mode, which prepares the body for action, and the parasympathetic ‘rest and digest’ mode, during which things like digestion, growth and repair are prioritised. In meditative practices like yoga, the body tends to favour the parasympathetic nervous mode, with a low heart rate and slowed breathing. This is in contrast to the sympathetic nervous system where heart and breathing rate speeds up. The autonomic nervous system has nerves by which brain controls the activity of various organs in the body. Likewise, there are other nerves that provide the brain with sensory information. By conscious control of our breathing, we alter the sensory information sent from the lungs to the brain. In response to this sensory information the brain enhances either the parasympathetic or sympathetic modes. It turns out that during yoga, the slow controlled breathing activates the parasympathetic mode.

The sympathetic mode responses are largely meditated by a hormone molecule called cortisol. While the sympathetic nervous system functions to prepare the body for action in life-threatening situations, it can also be activated by non-threatening stress signals. A text from your boss, bank statements, exams, and any other aspect of stressful 21st century living can activate the sympathetic mode. There is evidence that associates mood disorders, such as depression, with the neurotransmitter molecule serotonin. Evidence suggests that cortisol may also be important. Recent experiments have shown high levels of cortisol can damage nerve cells and switch on instructions for cellular suicide.  This may play a key role in contributing to symptoms of depression. Approximately one quarter of UK citizens experiencing mental health problems at some point in their lifetime. The many stresses we face in our modern world could increase the chances of mental health problems by sustaining an unnaturally over-active sympathetic nervous system and cortisol-induced damage.

So, where does yoga fit in? Yoga often depresses sympathetic mode activity while enhancing the parasympathetic mode – which could mean that yoga decreases cortisol levels. Neuroscientist, Thirhalli, and colleagues conducted an experiment on patients with depression and found that after four weeks of regular yoga practice, blood cortisol levels decreased. This correlated with a decrease in depressive symptoms. This may provide insight into our current mental health treatment plans. Antidepressants don’t work in up to thirty percent of patients and have negative side effects as well as unpleasant withdrawal symptoms. Encouraging patients to get involved with yogic and meditative practices, alongside psychological therapy, may be a good idea before immediately prescribing medication.

Beyond decreasing cortisol levels, yogic practices have shown to have other beneficial mental effects. One experiment demonstrated that yogic breathing techniques could increase levels of nerve growth factor – a molecule involved in repairing nerve cells which was shown to be deficient in Alzheimer’s patients. Other experiments have shown yoga can increase levels of oxytocin – a molecule key in social functioning and is deficient in schizophrenic patients. Quite often people hold their faith in science and have far much more trust in a chemical compound administered by a psychiatrist than in spiritual practice. However, with further research, science is proving that spirituality may have something to offer in terms of mental health. When Patanjali comprised the yoga sutras in 400 BC, he was not writing with it in mind of potential therapies for Alzheimer’s patients, but this does not mean modern medicine cannot learn from these practices.

Although modern Western yoga may be a total distortion from its roots, this should not discredit the fact that people are engaging in a practice that is good for their general physical and mental health. Science and spirituality can learn from each other and I for one think that the rise in yoga practice in such a stressful world is an excellent thing.



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