This is an example of one of the research projects that was done as part of the Yoga Teacher Training program. Each person chooses a subject to research and present. It is empowering for a yoga teacher to know that they can go ahead and investigate a topic and then know how to specifically apply the yoga technology toward that area.
YOGA AND DEPRESSION
Jane De Sousa
Depression is a word used colloquially to describe sadness and a feeling of being down and by mental health practitioners to describe a mood disorder and mental illness. Feeling sad and down in relation to events which happen in life is normal. The difference between normal healthy sadness and clinical depression is that normal sadness comes in waves with periods of happiness in between and does not affect a person’s self esteem, while in clinical depression a sense of sadness and lack of interest and pleasure in life is persistent and usually accompanied by feelings of worthlessness and self-loathing. In this paper I will explore the effect yoga can have on clinical depression.
In the field of mental health there are six types of depression – Major Depressive Disorder (MDD), Persistent Depressive Disorder (less severe than MDD), Melancholic Depression (lack of ability to experience pleasure), Seasonal Affective Disorder (related to change in weather in winter), Post-Partum Depression (related to pregnancy) and Psychotic Depression (depression accompanied by hallucinations and delusions). For the purpose of this paper I will look at the effect of yoga on Major Depressive Disorder as any affect yoga has on MDD will extend to Persistent Depressive Disorder and these are the most common types of clinical depression that can affect anyone of any age.
Major Depressive Disorder is a chronic mental disorder that causes changes in mood, thoughts, behaviour and physical health. A person is diagnosed with MDD when they have a persistent feeling of sadness during most of the day and at least 4 of the following symptoms for at least 2 weeks or more:
- Feeling of tiredness and lack of energy almost every day
- Feeling of worthlessness and guilt almost every day
- Difficulty thinking, concentrating and making decisions
- Cannot sleep or sleep too much
- Change in appetite leading to weight loss or gain
- Loss of interest and pleasure in activities once enjoyed
- Anxiety, agitation, restlessness
- Think often about death and suicide (not just the fear of death)
Current knowledge regarding the physiology of depression argues against a unified hypothesis of depression (Haster 2010). There is no one pathophysiology for MDD. It is not known exactly what causes depression and a variety of factors are thought to be involved – genetic, biological, environmental and psychological. The current neurobiological theories with the most valid empirical foundation and the highest clinical relevance are (Haster, Fetaku et al, Havard Health Publishing ):
- Genes and Psychosocial Stress – genetic vulnerability and environmental interaction.
Studies show that the influence of genetic factors in depression is 30 – 40% with non-genetic factors explaining the 60-70% variance in susceptibility to depression. Genetic factors make certain individuals susceptible to depression by increasing their vulnerability to stressful environmental factors.
- Stress Hormones – stress response circuits
Stress is an automatic response to any stimulus that requires a person to adjust to change. In the stress response hormones are released in response to the perception of psychological stress by the cortical brain regions triggering a chain of chemical reactions and responses in the body. The stress response starts with the secretion of certicotropin-releasing hormone (CRH) from the hypothalamus. Studies show that depressed people have increased CRH levels. Antidepressants and electroconvulsive therapy reduce CRH levels and as they drop depression symptoms are alleviated.
- Biogenic Monoamine Theory – mediating role of monoamines neurotransmitters
Monoamine neurotransmitters , such as serotonin and dopamine, are involved in a broad range of brain functions including mood, attention, sleep, appetite and cognition. A depletion of these neurotransmitters is linked to depression through the fact that drugs which help to increase the levels of these neurotransmitters either by blocking a monoamine degrading enzyme or by blocking the reuptake of the neurotransmitters into the presynaptic neuron are shown to alleviate depression.
- Neurotrophic Hypothesis – neural circuitry of depression
There is consistent evidence that there is a volume loss of the hippocampus and other brain regions in people who have suffered with depression for a period of time. This volume loss of the hippocampus results in increased stress sensitivity and risk of depression reoccurrence. This could explain why the first depressive episode is usually reactive and triggered by a clear psychological stressor, with subsequent episodes becoming increasingly endogenous, i.e. triggered by minor stressors or occurring spontaneously.
- Altered GABAergic Neurotransmission – reduced GABAergic activity
Gamma-aminobutyric acid (GABA) is a naturally occurring amino acid that acts as a neurotransmitter in the brain. It inhibits certain brain signals and decreases the activity of the nervous system. Studies show a reduction in the total GABA concentrations in the prefrontal and occipital cortex of the brain in people with depression. This reflects chronic stress in the body.
- Circadian Rhythm – sleep-wake regulation system
Disruption of circadian rhythms has been proposed to make individuals susceptible to depression. Manipulation of the circadian rhythms in depressed patients has been shown to have an anti-depressant effect. Melatonin, a hormone secreted by the pineal gland, regulates the rhythm of various biological parameters, such as body temperature, cortisol secretion (part of the stress response), and sleep cycles. Delayed circadian rhythms in people with depression has been linked to diminished levels of melatonergic signalling in the brain.
Traditional western medical treatments for depression are psychotherapy, antidepressant medications and electroconvulsive therapy. Generally psychotherapy alone is used for mild cases of depression, a combination of psychotherapy and antidepressants are used for moderate to severe cases of depression, and electroconvulsive therapy is used for severe depression that does not respond to the other treatments. Most individuals with MDD report only a 50% decrease in symptoms with the use of these standard treatments for depression. This has created interest in identifying and understanding alternate or complementary treatments.
Since the 1970s meditation and other stress reduction techniques such as yoga have been studied as possible treatments for depression. A number of systematic review articles (Mehta et al, Bridges et al, Cramer et al) state that the results of yoga interventions suggest that yoga can have long-term effects on depressive systems in various populations. Yoga is part of current research studying the effectiveness of mind-body interventions as an alternative and complementary treatment for depression. The scientific study of yoga has demonstrated that mental and physical health are not just closely allied, but are essentially equivalent. Studies have shown that no one type of yoga is more effective than another and that yoga is:
- effective in reducing mild depressive symptoms to major depressive disorder;
- comparable to both exercise and medication in reducing unipolar depressive symptoms;
- not more effective than conventional treatment methods but has the benefit of no side effects, no social stigma and accessibility;
- accumulative in its positive effects with yoga groups showing greater improvement of symptoms at 3 and 6 month follow ups compared to other treatments; and
- also effective when practiced for short periods.
Yoga was first studied as a possible alternative treatment for depression because it is stress-reducing. As depression often co-occurs with disorders associated with stress and the fact that the stress response is central to the understanding of the pathophysiology of depression, practices and techniques that assist to reduce stress are likely to reduce depressive symptoms. In order to understand how yoga can assist in reducing depressive symptoms, it is important to understand the stress response.
The brain determines what is threatening and stressful. When the brain perceives a threat the hypothamalus in the brain signals the pituitary gland and adrenal glands forming the hypothalamic-pituitary-adrenal (HPA) axis which governs a multitude of hormonal activities in the body that form the stress response. The hypothalamus secretes CRH which then does two things:
- Stimulates the pituitary gland to secrete adrenotrophic hormone which stimulates the adrenal glands to secrete adrenaline and cortisol which ready the body for ‘flight or fight’ with increased heart rate and blood pressure and sharpened senses. Adrenaline governs the short-term response to acute stress. As adrenaline levels drop, cortisol levels rise with cortisol governing the response to longer term stress. Cortisol builds up slowly and takes longer to be reabsorbed and return to normal levels.
- Affects the cerebral cortex, amygdale and brainstem which play a major role in coordinating thoughts, behaviours, emotional reactions and involuntary actions. Working along a variety of neural pathways CRH influences the concentration of neurotransmitters in the brain.
Chronic stress induces an imbalance in the autonomic nervous system with decreased parasympathetic nervous system (PNS) activity and increased sympathetic nervous system (SNS) activity; under activity of the inhibitory neurostransmitter GABA; and an increased allostatic load (wear and tear on the body as it tries to maintain stability during conditions that are outside the usual homeostatic range). Studies have shown that yoga is associated with changes in the following biologic markers consistent with stress reduction:
People with MDD have significantly lower levels of GABA compared with people who have no history of mental illness. Studies show an association between yoga practice and increased thalamic levels of GABA as well as improvements in mood and anxiety, suggesting that GABA may mediate the positive effects of yoga on mood.
People with MDD have higher levels of cortisol. A study has shown that after an 8 week yoga intervention there was a decreased cortisol reactivity to stress among participants who had had an elevated baseline reactivity.
Heart Rate Variability
The imbalance between the PNS and SNS generated by chronic stress results in a low heart rate variability (HRV) with low variability between heart beats. Studies show that yoga is associated with increased HRV indicating an overall improvement in the regulation of the autonomic nervous system.
Research shows that people with depression have a larger concentration of inflammatory cytokines in the central nervous system. Studies show that long-term yoga practitioners show decreased inflammatory markers when compared to new practitioners.
Streeter et al propose that the reason yoga is effective in reducing stress and therefore reducing depressive symptoms is because it directly increases the functioning of the PNS through the vagal nerve (10th cranial nerve and main peripheral pathway for parasympathetic control of the heart, lungs and digestive tract). Parges Polyvagal Theory identifies 3 phylogenetic developments in the neural regulation of the autonomic nervous system – the oldest unmyelinated visceral vagus which responds to threats by depressing metabolic activity; the SNS capable of increasing metabolic rate and mobilising behaviours necessary for ‘fight or flight’; and the most advanced myelinated vagus which promotes calm states consistent with metabolic demands of growth, repair and restoration, as well as supporting social engagement and engendering feelings of safety. Research shows that the myelinated vagal nerve allows more rapid adjustment of the heart rate and HRV than does SNS control, which takes longer to turn off and on. When this myelenated vagal break fails, the older SNS is used to regulate metabolic output in response to stress. This reduces flexibility of the response to threat and delays the return to a calm, reparative, anti-inflammatory state when the threat has ceased. An under activity of the PNS therefore leads to a greater dependence on the SNS with negative health consequences, including depression.
The relationship between yoga and PNS activity is most clearly demonstrated in studies of yoga breathing. Voluntary changes in breath pattern can account for 40% of variance in feelings of anger, fear, joy and sadness. Voluntary controlled breathing patterns can affect the autonomic nervous system and HRV. Brown and Gerbarg describe a neurophysiologic model for yoga breathing in which the stretch receptors in the alveoli, barorecptors, chemoreceptors and sensors throughout the respiratory structures send information about the state and activity of the respiratory system through vagal afferents (distinct lower motor and preganglionic parasympathetic fibres) and brainstem relay stations to other central nervous system structures where they influence perception, cognition, emotion regulation and somatic expression and behaviour. Because breathing is vital to survival, information from the respiratory system must be noticed and attended to immediately. This model therefore suggests that signals from vagal afferents carrying information regarding changes in the rate, depth and pattern of breathing receive the highest priority and have widespread effects on brain function. Streeter et al postulates that this is one model to explain how yoga practice can reduce imbalances in the autonomic neural system and so reduce depressive symptoms.
There is clear evidence that yoga is an effective treatment for depression and there is a possible physiological explanation for why this is so. However, yoga is not simply a physical exercise practice; it is also a spiritual philosophy. The philosophy of yoga has not been studied in relation to depression, but many modern yogis have explored this connection through their own practice. Amy Wientraub, a yoga practitioner who has spent many years using and researching yoga as a treatment for depression, links the effectiveness of yoga in treating depression with the spiritual philosophy of yoga. She explains that the ancient yogis believed we hold life’s traumas and losses in both our psychic (mental-emotional) body and our physical body. The body is therefore an important gateway for relieving mental health issues like depression. The physical practice of yoga assists in healing both the physical and psychic body and bringing them back into balance. Furthermore, present day yogis like Amy Wientraub believe that one of the reasons people get depressed is because they forget who they really are – a being intimately, eternally and deeply connected to all beings and to universal energy. When people forget this, they feel isolated and alone and depressed. There is no scientific study to prove that the above statements are true, yet based on my own experience of recovery from depression, they are exactly why yoga is such an effective treatment for depression as well as a practice that enables a person to live a balanced, contented life in which depression is no longer something to be feared or suffered.
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