Yoga Therapy: A Research Brief    Yoga Therapy A Research Brief  

      
   Executive Summary     Based on classical Indian yoga and its revival in the early twentieth century, yoga therapy is rapidly building esteem in the United States and Europe as a feasible, practical, and low-risk complementary intervention treatment for mental and physical health conditions, including cancer and musculoskeletal, neurological, endocrine, cardiovascular, and respiratory issues. Yoga therapy differs from conventional medicine, which primarily takes a biomedical approach that considers conditions in isolation and relies on pharmaceutical and surgical solutions. The biomedical approach has been effective in controlling infectious and communicable diseases such as smallpox, tuberculosis, and polio, but has proven less effective in treating non-communicable diseases such as heart disease, stroke, cancer, diabetes, and respiratory diseases, which cause the majority of deaths worldwide and are rapidly increasing in prevalence.1 Many non-communicable diseases are preventable through lifestyle modifications, particularly by reducing tobacco-use and alcohol consumption, increasing physical activity, adopting a healthy diet, and managing stress.2 While yoga is often seen as simply physical exercise, the classic “yogic lifestyle” taught by yoga therapists provides a holistic, mind-body approach to health and wellness. Established in 1989, the International Association of Yoga Therapists (IAYT) is the professional accrediting organization for yoga therapists. IAYT’s website explains that yoga therapy is a process for empowering individuals to improve their health and wellbeing, with an emphasis on changing clients’ relationships to and identification with their conditions. According to the IAYT, the goals of yoga therapy are “eliminating, reducing, or managing symptoms that cause suffering; improving function; helping to prevent the occurrence or recurrence of underlying causes of illness; and moving toward health and wellbeing.”3 Yoga therapy treats mental and physical health conditions as multifactorial, or arising from a complex intersection of individual circumstances. The multimodal treatment includes five main components customized for individual cases: (1) physical poses (asana), (2) breathing exercises, (3) meditation, (4) relaxation, and (5) Ayurvedic diet. The field of yoga therapy is continually adapting to conventional medical research expectations, including standardization and replication, but this remains challenging because yoga therapy is so highly customized. While many studies have found positive results related to yoga therapy, these findings are limited by research methodology, design, and size. Increased acceptance by medical institutions and the public will aid in securing more funding and expanding research of yoga therapy’s effectiveness beyond common health conditions. Additionally, technological advances will enable researchers to further explore the mechanisms of yoga therapy, specifically on cellular and molecular levels.       
   Introduction     The development of yoga therapy is a story of revival and modernization of ancient yoga practices. In the 1920s, during a period of rising Indian nationalism, yoga became popular as exercise for maintaining health and wellbeing.4 Three men—Sri Yogendra, Swami Kuvalayananda, and Tirumalai Krishnamacharya—were at the forefront of this movement, laying the foundation for yoga therapy. They began studying yoga for health and wellbeing using X-rays, air pressure, oxygen and carbon dioxide levels, acid/base balance, and blood pressure to assess the impact of poses and breath.5 Krishnamacharya became the most famous of these men internationally. He is regarded as the Father of Modern Yoga, and many yoga therapists today trace their lineage back to him. His students, including B.K.S. Iyengar, Pattabhi Jois, Indra Devi, and his son T.K.V. Desikachar, became influential yoga therapists.6   As the number of people practicing yoga and the number of national and international associations supporting yoga have grown since the 1980s, so too has acceptance of yoga therapy as an effective treatment within the field of conventional medicine in Europe and the United States.7 A particularly significant development occurred in 1990: U.S. healthcare insurance companies awarded coverage to Dean Ornish’s lifestyle program to reverse heart disease through a combination of yoga, meditation, and diet. A few years earlier, Ornish and colleagues published the results of the first double-blind clinical study to show that heart disease could be reversed through such a program.8 Since that time, the quantity and quality of yoga therapy research has continued to increase, leading to additional insurance industry advancements such as the 2012 decision to include yoga therapy as a covered treatment for heart disease under the U.S. Medicare program.9   Yoga therapy is based on creating balance: a yoga therapist is trained to treat clients by restoring equilibrium on the anatomical, physiological, intellectual, emotional, and spiritual levels, which are the five koshas, or dimensions of life, in classical yoga.10 To do this, a yoga therapist must conduct a detailed analysis of the client’s current state of mind, body, and spirit, as well as the client’s family situation, work environment, available leisure time, socio-economic level, and culture to create a personalized therapy plan that is be adaptable to changes in season, time of day, and various other fluctuations.11 Given this personalization and the wide angle of treatment, yoga therapy is usually delivered in one-on-one or small group sessions, where each client can easily receive individual help, rather than in large group sessions or studio yoga classes. A client is typically assigned a short daily practice, in addition to a weekly session with the therapist.12       
   Physical poses    The physical poses (asana) of yoga therapy are believed to promote physical and mental health by decreasing inflammation, stimulating the vagus nerve, and activating the brain to increase mind-body awareness and self-regulation. The types of poses and style of pose sequences used in yoga therapy can vary: some styles are fast-paced and dynamic with continuous movement, while other styles are slow-paced, emphasizing stillness and long holds. In addition yoga therapists often modify poses for different individuals. Regardless of this variability the use of  yoga poses in yoga therapy always emphasizes attention to stability, connection to breath, and focus on the mind-body relationship through sensing the internal state of the body and the position and movement of the body.
      
   Breathing exercises     Breathing exercises in yoga therapy are believed to release calming hormones, activate the autonomic nervous system, strengthen the respiratory system, and increase self-regulation. Yoga therapists commonly teach breathing techniques and practices during sessions, and clients then perform the exercises daily between therapy sessions. There is great variety in yogic breathing exercises, for example: breath may be through the mouth, nose, or alternate nostrils; may be fast or slow; deep or shallow; continuous or including retention; and linked with movement or independent. Breathing exercises are an accessible therapeutic intervention for most people, including children, elderly, and those with physical limitations, who may not be able to perform physical poses.       
   Meditation     Meditation is the disciplined practice of attention regulation, which is believed to help decrease chronic pain and cancer symptoms and promote healthy aging through metacognitive awareness, attention to bodily sensation, and moving away from self-evaluation. While meditation may be practiced in a variety of ways, it typically includes mental training that develops self-awareness, self-regulation, and self-transcendence, or shifting the focus away from self onto others.13 In yoga therapy, meditation is used as a tool for gradually expanding the attention. For example, clients may be asked to focus on the breath as a single element, then gradually incorporate other elements as their practice progresses, simultaneously monitoring the breath, the body, sensation, etc. Common types of meditation used in yoga therapy include body-scan meditation, mindfulness meditation, guided imagery meditation, and sound or mantra meditation, also called transcendental meditation.14       
   Relaxation     Relaxation techniques in yoga therapy are incorporated in many different ways. They can be incorporated into asana practice as a final resting pose, integrated throughout a multimodal practice, or independently practiced. These techniques are believed to promote mental health, positive wellbeing, and women’s health by balancing hormone levels, stimulating brain waves, and activating the autonomic nervous system. One type of yogic relaxation practice is yoga nidra, which typically combines breath awareness, meditation, and guided visualization to progress from deep relaxation to a near sleep-like state.15 Such relaxation interventions are considered highly feasible and practical, as they can be adapted across populations and settings, including community, educational, and hospital settings.16       
   Ayurvedic diet     Ayurveda is India’s traditional whole-body healing system based on balancing mind, body, and spirit. Under the Ayurvedic system, people are made up of five basic elements: earth, water, fire, air, and space. These combine to form three life forces called doshas that control the body: Vata dosha (space and air); Pitta dosha (fire and water); and Kapha dosha (water and earth). Individuals have one or two dominant types of doshas, which should be regulated for good health through diet and lifestyle based on changes in time of day, year, and life.17 Ayurveda is considered to be a sister science of yoga, but is less popular and less researched in conventional U.S. and European medicine. It is most commonly studied for weight control and related disease.       
   Key Findings           
   Health Benefits of Physical Poses    The physical poses and pose sequences included in yoga therapy show similar health outcomes as other forms of physical activity. Many yoga styles and postures are weight-bearing and thus beneficial for bone growth and osteogenesis.18 For example, the common pose sequence known as Sun Salutation A includes standing poses along with downward facing dog and plank poses that put weight on the hands. Movement-based yoga styles also improve muscular strength and endurance, flexibility, and cardio-respiratory health.19 Generally, however, yoga asana is a less demanding form of aerobic exercise, which means that a physical yoga practice may be less effective for maintaining and improving cardiovascular fitness than other forms of exercise, unless the yoga practice includes rigorous, dynamic movements.20 Studies have shown that compared to conventional resistance-based exercise, yoga asana is equally or more effective for mental health as measured by fatigue, self-esteem, quality of life, and depression.21 In a study that compared yoga asana with walking—an exercise form that is similarly demanding on the cardiovascular system—yoga was more effective in improving mood and decreasing anxiety.22 Additionally, there is some support that good musculoskeletal alignment, as taught in yoga asana, can affect pain tolerance and encourage positive thinking.23 Studies show that yoga asana may activate particular parts of the brain and the basal ganglia circuits, which promote motor abilities, learning, cognition, and emotion, and this activation may explain the creation of a mind-body connection and self-regulation from yoga asana practice.24
      
   Breathing & Relaxation Techniques    A yoga therapist may assign particular breath patterns to yield specific emotional and physiological effects. Slow, rhythmic breathing exercises promote parasympathetic activation to relax the body and the mind, while forceful breathing exercises promote sympathetic activation in preparation for movement.25 A popular breathing technique in modern yoga is called ujjayi breathing, which emphasizes a deep slow breath through the nose at a steady pace, with a soft throat constriction that creates a gentle sound.26 Yoga therapists often recommend slow breathing exercises to decrease stress and anxiety. Disordered breathing produces and maintains symptoms across a spectrum of anxiety disorders, but slow diaphragmatic breathing reduces psychological distress and symptoms of hyperventilation, helping the client regain a sense of self-control.27 Yogic breathing techniques have been found to help with trauma recovery for anxiety-related dysfunction of the autonomic nervous system in people with post-traumatic stress disorder (PTSD) by slowing the breathing rate down to six breaths per minute, which decreases oxidative stress.28 The benefits of slow breath may be related to the physiological effect of releasing prolactin and oxytocin, which promotes feelings of calmness and social connection.29 Across studies, the relaxation techniques used in yoga therapy have been found more effective than multimodal practices for anxiety-related disorders.30 A study on yoga nidra and anxiety found that yoga nidra was more effective than seated meditation for reducing both cognitive and physiological symptoms of anxiety.31 Yoga nida has also been shown to to reduce stress, depression, and worry, as well as increase mindfulness.32 While medical and health care practitioners sometimes discourage clients with trauma from practicing yoga nidra due to trauma flashbacks that can happen while falling asleep, a special form called Integrative Restoration, or iRest, has been helpful in decreasing PTSD symptoms, negative thoughts of self-blame, and depression for clients with PTSD, veterans, and women with sexual trauma.33
      
   Yoga Promotes Healthy Organ Function    Targeted use of asana for particular organs has not been fully explored or supported in research; however, there is preliminary research suggesting that particular poses—including sarvangasana (shoulder stand), matsyasana (fish pose), marjariasana (cat pose), halasana (plow pose), and bhujangasana (cobra pose)—ease hypothyroidism by stimulating the thyroid through compressing and stretching.34 More evidence is needed to determine the impact of specific poses on health and wellbeing. Research shows that prolonged stretching, performed in many yoga poses, is linked to immune health and tissue fluid regulation, which can decrease inflammation and promote organ functioning.35 Yoga asana may also stimulate the vagus nerve, which regulates the heart, lungs, and digestive system, as well as muscles in the face and mouth, including those used for speaking. Slow breath may also promote heart health by reducing hypertension and heart disease. In yoga therapy, hypertension is perceived to be the result of a high-stress lifestyle, and affected clients may need additional coaching to adopt a positive attitude and yogic lifestyle modifications, both of which can be connected to the breath. Yogic breathing exercises have also been shown to promote respiratory health, improve heart rate variability (the time it takes the heart rate to return to normal after excitement), and increase self-regulation.36 Studies show that alternate nostril breathing activates the parasympathetic nervous system and decreases systolic blood pressure.37 The benefits of slow breath for heart health are linked to increased vagal connections between the heart and the autonomic nervous system, and by reducing stress through increased emotional regulation, or the ability to effectively modulate one’s emotions or behavior.38 In addition to slow breath, faster breathing exercises may benefit heart health by strengthening the respiratory system.39
      
   Chronic pain Treatment    Chronic pain is pain that has been present for at least six months and may or may not have a known cause. It may manifest in the form of lower back pain, headaches, arthritis, fibromyalgia, and other conditions. Side effects of chronic pain cause significant disruptions, including sleep disturbances, decreased functional capacity, depression, and decreased quality of life.40   The majority of research on yogic meditation and chronic pain involves a well-known program called Mindfulness-Based Stress Reduction, which includes mindfulness meditation, body scan meditation, and gentle yoga to promote self-regulation and to give the client control over pain. These studies have found that yogic meditation helps ease the burden of both short- and long-term effects of chronic pain in the general population.41 Some studies have examined meditation as a yoga therapy treatment for particular conditions or special populations, such as the elderly or underprivileged groups; future research will give more attention to these topics.42 Yoga therapy meditation may also help with cancer-related symptoms and short- and long-term side effects. Some side effects of cancer beyond chronic pain include stress, depression, sleep disturbances, fatigue, nausea, vomiting, and chemotherapy-induced immunosuppression. Across studies, mindfulness meditation has been positively associated with a significant improvement in quality of life and reduction of pain, anxiety, stress, and depression in cancer patients.43 The majority of cancer studies focus on breast cancer, where meditation has positive immediate effects on quality of life, fatigue, sleep, stress, depression, anxiety, and feelings of safety, with long-term effects related to anxiety lasting after 12 months.44 Though limited, there is evidence that suggests yogic meditation is beneficial for cancer patients through cellular level impacts that reduce inflammation, promote cell-mediated immunity, and slow biological aging.45 Future research will further investigate the mechanisms of yogic meditation across cancer types.
      
   Weight Control    Ayurveda connects weight gain with the elements of earth and water, which have heavy, dense, slow, and cold qualities. These qualities cause poor digestion, low metabolism, overeating, sedentariness, excess sleep, depression, and anxiety. In a study on Ayurvedic treatment for obesity, 12 obese adults participated in a three-month Ayurveda and yoga therapy program tailored to their individual constitutions. Assessments were taken at three, six, and nine months, showing steadily decreasing BMI (body fat percentage) and waist-to-hip ratios. Additionally, their self-efficacy scores increased while their perceived stress decreased.46 Ayurvedic-inspired weight management may have long-term efficacy, as demonstrated in another study, because it improves psychosocial health through lifestyle changes, including mindful eating and improved body image, self-efficacy, body awareness, and self-compassion.47 Ayurveda has been shown to improve weight control and impact related disorders, such as cardiovascular disease, metabolic syndrome, and diabetes. In a study of 157 men newly diagnosed with Type 2 diabetes, an Ayurvedic diet including fresh herbal juices showed an improvement in blood glucose and hemoglobin levels.48 For people who are overweight, Ayurveda aids in weight loss, and for people who are underweight, Ayurveda aids in weight gain. In a study of 57 malnourished Indian children aged two to six years old, the children in the experimental group ate an Ayurvedic diet for two months while the children in the control group ate a standard diet. At the end of the study, the children eating the Ayurvedic diet showed significant health and weight improvements compared to the control group.49
      
   Different Populations.    Yoga therapy may be particularly effective in treating certain populations.
      
   Children    Breathing exercises are a popular form of yoga therapy for children, given the overall safety and simplicity that makes the exercises accessible. In 2017, the National Health Interview Survey reported an increase from 3.1 percent to 8.4 percent of children using yoga for health purposes.50 Very young children may be taught yogic breathing to avoid temper tantrums, create calmness, or aid sleep.51 For youth of all ages, conscious breath regulation can enhance energy and induce calmness, and can be performed anywhere and anytime, such as prior to school testing.52 Additionally, yogic breathing may be an effective intervention for specific childhood conditions. For example, children with Duchenne muscular dystrophy showed significantly improved pulmonary function after 10 months of yogic breathing.53 As many adult diseases originate from lifestyle and stress, yoga therapy-based programs in schools may prevent future illness by helping children improve self-regulation, stress-coping skills, resiliency, and mood.54 For this population, yogic breathing may help decrease stress, release calming chemicals, build vagal connections, strengthen the cardiovascular system, teach self-regulation, and more. Preliminary studies suggest that yoga is a better, more feasible alternative than physical education for schoolchildren’s mental health, particularly for underprivileged youths.55 Studies have also shown the effectiveness of yoga therapy’s relaxation exercises on this population. In a study of adolescents who participated in 30-minute sessions held three times a week for one month, yoga nidra increased measures of happiness, perceived stress, quality of life, and general wellbeing, including enthusiasm, alertness, self-control, self-confidence, and self-awareness.56 These studies are promising, but more research is necessary to draw stronger conclusions.
      
   The elderly     Meditation may be a particularly effective yoga therapy tool for aging clients, given its benefits and accessibility. Meditation appears to ease the aging process and slows decline in cognitive functioning. On the cellular level, yogic meditation has been associated with increases in telomerase activity that reduces cellular aging and reductions in aging-related chronic inflammation and immune system decline.57 Yogic meditation may also promotes brain health for the elderly by improving sleep, reducing neurodegeneration, and preventing cognitive decline.58 Further, brief, daily yogic meditations in the elderly may lead to improved mental and cognitive functioning and a decrease in depression.59 Future research will study yoga therapy programs for particular aging-related conditions.   Especially helpful for the elderly population, yoga therapy meditation may improve attention, awareness, sensory processing, self-regulation, stress, immune function, blood pressure, pain, and sleep.60 The benefits of meditation are connected to metacognitive awareness, or the conscious monitoring of mental processes to decrease the mind from wandering;61 attention to bodily sensations and sensory experiences, which promotes self-regulation and an increased ability to notice emotions without getting caught up in them;62 and reductions in self-evaluation and self-judgment, which help reduce depression and self-identification with negative thoughts.63       
   Women     Yoga therapists often recommend yoga nidra for women’s health, particularly in managing common side effects of menstrual disorders. One study found that after six months of yoga nidra, clients with menstrual disorders saw significant improvement in moderate anxiety and depression symptoms, but not in severe anxiety and depression symptoms.64 Another study of menstrual disorders found that compared to the control group, after six months of yoga nidra, clients with menstrual disorders saw improved scores in anxiety, depression, wellbeing, general health, and vitality.65 The positive effect of yoga nidra on menstrual disorders may be attributed to the rebalancing of hormone levels through the relaxation process. In one study, levels of thyroid-stimulating hormones, follicle-stimulating hormones, luteinizing hormones, and prolactin levels decreased significantly after yoga nidra had been practiced for 35 to 40 minutes per day, five times per week, over the course of six months.66 While more research is needed, these studies suggest that yoga nidra is effective as a complementary therapy to conventional pharmacological treatments for menstrual disorders.       
   Critical Evaluations     Yoga therapy treatments for the prevention, treatment, and rehabilitation of medical conditions are subject to many research challenges. Yoga therapy is an even “younger” field in conventional U.S. and European medicine than general yoga interventions.67 Most yoga therapy studies have been conducted as feasibility trials and single-arm pilot studies. The few randomized controlled trials (RCTs) have typically had small sample sizes and comparisons to “usual care,” which are ineffective for determining if outcomes can be directly attributed to the therapy or to related factors such as support and attention.68 Studies will draw stronger conclusions if therapy groups are compared to an active control group or an attention control group, rather than usual care or a waitlist group. Given the favorable outcomes of existing RCTs, and the few adverse events, it is timely to expand to larger trials on the efficacy and effectiveness of yoga therapy treatments. Yoga therapy research also faces design issues related to reporting--studies often lack detailed descriptions of therapy protocols and the training and background of the therapists.69 Client home practice also needs to be better monitored and described as executed, as independent regular or daily practice is necessary in yoga therapy. This may be improved through increased video-recording of yoga therapy sessions and home practice, as done in other health interventions.70 The expansion of yoga therapy research into large, robust studies with improved research design requires funding, which is limited, as there are only a few government and university institutions worldwide that financially support yoga research. Perhaps the biggest challenge for yoga therapy research is the difficulty of standardization. Research is expected to be replicable, but yoga therapy is necessarily individualized. If the therapy treatment were a one-size-fits-all, it would no longer be yoga therapy. Standardization could jeopardize the reputation of yoga therapy, as routines designed to treat a particular individual’s imbalances may prove ineffective if replicated. The profession of yoga therapy is confronting similar obstacles around standardization as it undergoes explosive growth. Organizations like the IAYT and the Council for Yoga Accreditation International in India are beginning to regulate accreditation, certification, and continuing education, but there has been little government oversight of who can call themselves a yoga therapist. In the United States, this poses hurdles for healthcare provider client referrals to yoga therapists and health insurance coverage of many yoga therapy interventions. There is debate over the advantages of accepting insurance as a yoga therapist because joining the healthcare system may reduce quality of care by limiting the contact between therapist and client.71       
   Future Directions     In addition to addressing challenges related to standardization and replication, the field of yoga therapy research needs to move beyond common health disorders to investigate the treatment’s efficacy with respect to a broader range of conditions. New areas of yoga therapy research already seeing growth include schizophrenia, post-traumatic stress disorder, irritable bowel syndrome, stroke recovery, and restless leg syndrome. Additional areas currently experiencing research growth include studies on yoga as preventive medicine, the effects of long-term yoga practices, and yoga in school and workplace settings. Many additional conditions, populations, and settings still deserve closer attention, including yoga therapy for pregnancy and for pre- and post-natal women. Another area ripe for future research is the effect of yoga therapy on positive psychology beyond diseases and disorders. As brain imaging research on various contemplative practices undergoes exponential growth, scientific understanding of the biomedical mechanisms underlying yoga therapy is also rapidly improving. Technologically-advanced imaging techniques have begun to show yoga-induced changes in brain functioning, including changes in brain structure and neurochemistry over time.72 The ability to measure change on the molecular level—for example, changes in gene expression, which have been shown to impact stress, inflammation, and immune function—and the precision and efficacy of such measurements opens other avenues for future research.73 Related to research design challenges, future research on yoga therapy should further explore integrating quantitative and qualitative methods to better capture the firsthand experience of the client and the working relationship between the client and yoga therapist.       
   Conclusions     Although confirming empirical evidence is limited and tentative, yoga therapy has become a feasible, practical, low-risk intervention for preventative healthcare and a complementary treatment for many conditions. This field has tested the limits of what counts as evidence in medicine and will lead the way for expanding horizons in complementary and alternative medicine. It’s important to note that yoga therapy should only be pursued with a trained and accredited yoga therapist who can assess the client and individualize the treatment for a therapeutic approach that is safe and effective.       
   Yoga therapy Yogic Breathing Exercises    Ujjayi a deep slow breath through the nose at a steady pace, with a soft throat constriction that creates a gentle sound Kapalabhati  rapid abdominal breathing involving short and forceful contraction of the anterior abdominal wall Bhastrika rapid thoracic breathing using intercostal and accessory muscles Sitali pranayama slow breathing through puckered lips with a curled tongue Nadi shodhana alternate nostril breathing Kumbhaka retention of the breath for various durations either after inhalations, exhalations, or both       
   Footnotes    
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