CU Research Brief - Yoga Interventions

Executive Summary

Yoga has evolved from an ancient practice in India to a popular health trend in the United States and Europe. As yoga has grown and spread, it has multiplied into diverse styles practiced for distinct purposes. Despite such broad variations, practitioners of almost all types of yoga report increased wellbeing. There is a growing evidence supporting such claims, but most findings are still tentative given the relatively recent rapid expansion of yoga research since 2000. Research does show that yoga is a feasible, practical, low-risk intervention as a complementary therapy for many physical and mental health conditions.

This brief provides an overview of the current state of research on yoga interventions, for mental, physical, and cardiovascular health and for autoimmune and other disorders. These interventions may be particularly beneficial for the elderly, though they should be practiced with caution by vulnerable groups. Yoga is an adaptable practice—it may be done seated in a chair or lying on the floor— and so far, there is little evidence to suggest that one style is better or more effective overall than others. Additionally, few adverse events from yoga interventions have been reported.

Research on yoga interventions has become more rigorous over time, with an increase in randomized controlled trials and improved reporting on yoga style and “dosage”; nonetheless, methodological challenges persist. Yoga may be a particularly difficult topic to study compared to typical medical interventions, given the difficulty of defining yoga styles and dosages, the reliance on self-reporting, and methodological variety. Researchers continue to refine their methodology as well as expand the study of yoga into other areas such as in connection with children, less common conditions, and issues of cost-effectiveness and cultural perceptions.

Introduction

The ancient practice of yoga is rooted in Indian philosophy and spirituality thousands of years old. Over the past decades, yoga has been adapted into a modern secular practice popular in the United States and increasingly of interest for health and wellness. Modern yoga is a combination of physical postures, breathing techniques, meditation, concentration, and relaxation. According to a 2016 study, about 11% of U.S. adults had practiced yoga that year and about 28% had practiced yoga at least once in their lives.^[1] About 80% of them reported starting yoga explicitly to improve their health.^[2]

Research on medical yoga interventions is expanding to determine if yoga yields benefits beyond increased flexibility and muscle tone and may be used as a preventative measure and a treatment for a range of medical conditions. Compared to pharmaceutical treatments, yoga may be more appealing because it’s less invasive and may be safer and have fewer side effects. Yoga may be particularly useful as an intervention for non-communicable diseases such as cardiovascular and respiratory diseases, cancer, and diabetes because they are attributed, in part, to lifestyle factors, including tobacco use, lack of exercise, and stress.^[3] While more research is needed, yoga appears to help reduce inflammation, stress, and depression. Yoga may also improve blood glucose levels, cardiovascular function, hormone regulation, and self-confidence. 

In this brief we provide an overview and critical evaluation of the latest research on yoga as a mental and physical health intervention. These studies cover a breadth of topics and involve a variety of methods. While offering many promising findings, this diversity is also a weakness. Greater standardization of studies with more rigorous procedures and reporting would offer more conclusive evidence of yoga’s benefits. Following our summary of key findings, we discuss future research directions in the field.

Key Findings

Research on yoga as a medical intervention is rapidly growing. Over 200 studies have been published yearly since 2011.^[4] A total of 29 different countries have hosted such studies, but India leads the way with twice as many published research articles on yoga as the United States.^[5] These studies have explored a wide range of topics, the most common of which include yoga as treatment for depression, anxiety, low back pain, hypertension, multiple sclerosis, breast cancer, and elderly fitness. About 85% of published studies involved adults who report to have medical conditions.^[6] Although this research has covered 52 different styles of yoga, Hatha yoga (a category of yoga styles that focus on poses, the body, and alignment) has been the most popular intervention, used in 11% of the studies. The median length of yoga interventions studied was nine weeks.^[7]

Findings shared below are grouped into five categories of health and wellness concerns for which yoga has been studied as an intervention: (1) mental health, (2) physical health, (3) cardiovascular health, (4) autoimmune diseases, and (5) other diseases. Many of these findings indicate positive trends, but they are tentative or inconclusive due to study limitations, including design, sample size, and methodology. 

Yoga and Mental Health

Yoga has a positive effect on mental health, but there are conflicting findings on the significance of this effect.^[8] While research is limited and efficacy varies, yoga offers some benefit in treating mental illness.

The impact of yoga on overall mental health and as a treatment for mental illness has become a topic of great popular and clinical interest over the past 15 years.^[9] Yoga practitioners typically report a positive effect on their mental health as a result of their practice, and research tends to confirm that yoga impacts participants’ psychological wellbeing and may increase their levels of self-compassion and self-esteem and their relaxation and coping skills.[10] Yoga also may help practitioners increase or maintain their ability to thrive despite adversity—i.e., their resilience.^[11] While research suggests that practicing yoga does impart some mental health benefits, however, a meta-analysis of many of these studies found that yoga had no statistically significant effect on improving overall life satisfaction or social relationships, based on a cumulative analysis of randomized controlled trials.^[12]

Regarding mental illness, research shows yoga may be effective as an acceptable, feasible, practical, and low-risk intervention, but evidence for this is inconclusive and depends on the illness.^[13] Studies have shown yoga may be most successful as a treatment for depression, but its effect is comparable to exercise and medication.^[14] Findings show that yoga, similar to other forms of exercise, may decrease levels of the stress hormone cortisol, which in turn leads to a decrease in depression.^[15] Similarly, practicing yoga may alleviate perinatal depression.^[16]

There is a paucity of research on yoga as a treatment for other mental health conditions and results have been limited. However, there is some evidence supporting yoga as a primary or ancillary treatment for ADHD; anxiety disorders including generalized anxiety, panic, and obsessive-compulsive disorders; post-traumatic stress disorder; and distress-related overeating.^[17]

The lack of conclusive evidence related to yoga and mental health may be surprising given all the popular anecdotes about the benefits of yoga, but length constraints in research studies may be one reason for limited findings. For example, some studies suggest that the mental health benefit of yoga is cumulative over time and therefore may not be evident in a study lasting only two months.^[18] Another article suggests that the research process is complicated by a seasonal increase in anxiety and depression during the winter, which “buffers” positive findings.^[19] Another possibility is that the models of positive mental health typically used in psychological assessments do not adequately account for the kind of personal attributes rooted in yoga philosophy, such as meaning, wisdom, and detachment.^[20]

Yoga and Physical Health

Yoga is a beneficial medical intervention for many physical conditions, including low back pain, arthritis, and insomnia and is particularly promising as a treatment in elderly populations. Its impact on physical health may be attributed to reduced pain and inflammation and increased strength, flexibility, and cognitive function.

Modern yoga has many physical benefits similar to exercise, and, for the elderly, it may be superior to other forms of exercise for building aerobic fitness and strength, balance, and mobility.^[21] Across the adult lifespan, types of yoga based on stretching, such as Thai yoga and Hatha yoga, increase overall flexibility and, notably, spine flexibility.^[22] Yoga is widely regarded as an effective treatment for low back pain, for both decreasing pain and restoring functionality over time.^[23] Yoga is also a beneficial intervention for other inflammatory conditions of the soft tissues, including rheumatoid arthritis, fibromyalgia, osteoarthritis, carpal tunnel, and kyphosis.^[24] Yoga’s success in treating these physical conditions may be attributed in part to increased strength from the practice, especially from the more athletic forms of yoga such as Vinyasa yoga and Power yoga.^[25]

Also, the deep intentional breathing that accompanies yoga practice--called yogic breathing--even when practiced without physical poses has been shown to improve respiratory muscle.^[26]

Modern yoga has not been shown to lead to significant weight loss or a decrease in body fat percentage for healthy adults. However, adopting a traditional yogic lifestyle, including a vegetarian diet and a regular daily yoga practice over a long duration, may have a greater effect on weight and body composition.^[27] For overweight and obese people, practicing yoga can reduce body mass index.^[28]

Exercise in general is not only good for the body, but also good for the brain, and because of its emphasis on active attention during physical poses and yogic breathing, yoga may yield even greater cognitive function benefits than other forms of exercise.^[29] For example, across several studies on the impact of Hatha yoga, healthy adults showed improvement in self-control, working memory, attention, and processing speed.^[30] While fewer studies have been done on children and adolescents, yoga seems promising for fostering the self-discipline necessary for academic success.^[31] Yoga doesn’t only impact brain function during the daytime; it may help the brain relax during the nighttime. For older adults, yoga has been shown as an effective intervention for increasing sleep quality, sleep quantity and efficiency, and self-assessed feelings of well-restedness.^[32] For a wider population, yoga is beneficial for improving sleep, including in people with insomnia and cancer. However, yoga may be less impactful in cases of severe insomnia and with respect to less athletic types of yoga.^[33]

Beyond enhanced flexibility and strength, there are several other explanations for the impact of yoga as a medical intervention on physical conditions. One explanation is that yoga improves cognitive function and that increased mind-body awareness, self-confidence, and sleep from practicing yoga reduces pain.^[34] In a related study using magnetic resonance imaging (MRI), experienced yoga practitioners showed increased brain grey matter, correlating with increased cognitive function, compared to people who did not practice yoga, and this enabled the experienced practitioners to tolerate pain more than twice as long as the non-practitioners.^[35]

A second explanation for yoga’s impact on physical health is based on brain chemistry. Practicing yoga increases levels of serotonin and brain-derived neurotrophic factor proteins that reduce depression, but also reduces chronic pain by lessening the sensory nervous system’s response to stimulation.^[36]

A third explanation is based on decreased inflammation. Similar to other forms of exercise, practicing yoga decreases unhealthy inflammation that causes pain. Significantly, this effect can be achieved at lower levels of yoga-related physical activity than with other forms of exercise.^[37]

Yoga and Cardiovascular Health

Practicing yoga promotes cardiovascular health and reduces the risk of cardiovascular disease, Yoga is as effective as exercise for lowering blood pressure and improving lipoprotein levels, and may be particularly beneficial for at-risk populations as a safe, low-impact intervention.

Cardiovascular health is linked to mental and physical health. As such, the findings discussed in the previous two sections on yoga as a medical intervention for mental and physical health have relevance on cardiovascular health as well.[38] Cardiovascular health also has its own set of risk factors, including blood pressure, heart rate, lipids levels, and insulin resistance, which have drawn attention in medical yoga research as cardiovascular disease mortality rates have increased.^[39] Researchers find that on average the effect of yoga is comparable or superior to common physician-endorsed interventions such as exercise or lifestyle changes for mitigating cardiovascular disease risk factors.^[40]

Yoga primarily helps to reduce cardiovascular disease risk by reducing blood pressure. For example, it has been used as an intervention for people with prehypertension--which is elevated blood pressure at a level that indicates a risk for developing actual hypertension, i.e., abnormally high blood pressure. As a pre-hypertension treatment, yoga helps reduce both systolic and diastolic blood pressure in people over 40 years old.^[41] Studies have shown yoga to be beneficial in lowering blood pressure as a hypertension treatment. Studies have also shown that it is more effective than prescribed drug treatments and that active forms are as effective as general exercise.^[42] These benefits are attributed to increased parasympathetic activity, which counteracts excessive activity in the sympathetic nervous system.^[43]

Practicing yoga also lowers the heart rate.^[44] In one study, 13 participants lowered their blood pressure to normal rates after 3 months of lifestyle changes and practicing yoga, compared to only 4 participants in another group who only made lifestyle changes during that time. Another study showed yoga to be more effective in lowering diastolic blood pressure than non-aerobic exercise.^[45]

Another way that yoga has been shown to reduce cardiovascular disease risk is by reducing metabolic syndrome indicators, a cluster of factors linked to insulin resistance which precedes cardiovascular disease and Type 2 diabetes. These factors are fasting blood glucose, waist circumference (or abdominal obesity), blood pressure, high-density lipoproteins, and triglycerides; related factors include respiratory rate, waist/hip ratio, total cholesterol, glycated hemoglobin, and insulin resistance.^[46] The variety of conditions and the variety of yoga treatments makes it impossible to draw a simple conclusion, but consistently across studies, practicing yoga is better than no treatment and better than typical lifestyle modifications in healthy and at-risk populations.^[47] Compared to exercise, practicing yoga resulted in greater improvements in high-density lipoproteins, low-density lipoproteins, and very low-density lipoproteins.^[48] As treatment for these conditions, a higher dosage of yoga—practicing more frequently, for more minutes at a time—had greater effect than a lower dosage over more weeks or months.^[49]

The beneficial impact of yoga on cardiovascular health makes it an attractive option for prevention and treatment of cardiovascular disease, particularly for at-risk populations. Older adults, for example, have increased risk for cardiovascular disease and metabolic syndrome indicators, but only 8% of older adults meet safety guidelines for prescribing aerobic and strengthening physical activity to lower that risk.^[50] Yoga appears to provide a low-impact, safe alternative to exercise for improving blood pressure, body composition, glucose, lipids, endurance, and strength in older adults.^[51] Another at-risk population for cardiovascular disease are people with Type 2 diabetes. They experience similar benefits from practicing yoga as healthy people, with the greatest improvement in lipoprotein levels. There is also evidence that practicing yoga and yogic-style breathing increases quality of life and self-discipline in people with Type 2 diabetes, which aids them in managing the disease, including glucose levels.^[52] Some research has been done on African American women, an at-risk population for metabolic syndrome, and across studies, yoga shows positive effects on blood pressure, body weight, stress, and anxiety. More research is needed, however.^[53]

Yoga and Autoimmune Disorders

While yoga will not cure chronic autoimmune disorders, it does help patients manage symptoms. Significantly for these conditions, practicing yoga lowers unhealthy inflammation and stress.

Autoimmune disorders are chronic conditions in which the immune system attacks healthy cells as if they are foreign bacteria or viruses. Autoimmune disorder cases are now increasing, making prevention and treatment more important, but the cause for this increase is unclear. Research suggests the rise may be related to chemical environmental factors including high-fat, high-sugar, highly processed foods, and/or decreased microbial exposure.^[54]

There are over 80 autoimmune disorders with a diverse range of symptoms, but many of them are linked to unhealthy inflammation. As previously mentioned, yoga has been shown to help reduce inflammation even more effectively than exercise.^[55] Yoga also may help sufferers of these disorders by reducing stress, which aggravates the condition.^[56] This brief has already touched on yoga interventions related to two autoimmune disorders— rheumatoid arthritis and Type 2 diabetes. Below are findings on select additional autoimmune disorders.

Multiple Sclerosis, Fibromyalgia, Lupus, and Chronic Fatigue

These autoimmune disorders affect the entire body and have some shared symptoms: fatigue, pain, depression, impaired mobility, and impaired cognition. Multiple sclerosis (MS) is the most common of these disorders, impacting over 2.3 million people worldwide.^[57] MS is also the most studied, including with respect to yoga as a medical intervention. Across such studies, yoga showed greater improvements to fatigue and mood symptoms than conventional care, and compared to exercise, practicing yoga yielded a higher quality of life and faster reaction time in cognitive testing.^[58]

Similar results were found for yoga interventions on fibromyalgia. Compared to conventional treatment and other meditative movement therapies (tai chi and qigong), yoga led to significant improvements in pain, fatigue, depression, and overall quality of life. However, the small number of studies weakens the strength of these findings.^[59] Likewise, for lupus and chronic fatigue, yoga appears to be promising as a complementary treatment for symptoms, though more studies are needed.^[60]

COPD and Asthma

These belong to a group of autoimmune disorders that target particular systems within the body. In the case of asthma and chronic obstructive pulmonary disease (COPD), it is the cardiovascular system. While the causes of asthma and COPD are different, the symptoms are the same: chronic coughing and wheezing from airway hypersensitivity and shortness of breath. Evidence suggests that yoga helps control these symptoms in both disorders. In asthma, for both children and adults, yoga has been shown to increase lung function, forced expiratory volume, and quality of life sufficiently enough for yoga to serve as an ancillary treatment.^[61] With COPD, yoga has been correlated with increased lung function, forced expiratory volume, and physical activity capability sufficiently enough for it to become an ancillary treatment.^[62] For both asthma and COPD, the benefits of yoga can be attributed in part to yogic-style deep breathing, which increases respiratory stamina and calms the sympathetic nervous system.^[63] More research on these disorders could strengthen the findings.

Disorders Affecting Specific Organs

These disorders include those that target the gastrointestinal tract, such as inflammatory bowel symptom (IBS) and diseases (IBD), and the thyroid, such as Grave’s disease and Hashimoto’s disease. For IBS and related autoimmune diseases, including Crohn’s disease and ulcerative colitis, studies show that practicing yoga is as effective as medication for managing pain and anxiety while building self-efficacy and quality of life. However, it does not reduce disease activity.^[64] This research has focused mostly on adults with IBS and IBD, and while some work has been done on children and adolescents, those findings are more limited despite the potential for yoga as a safe adjunct therapy.[65]

For thyroid diseases, including hyperthyroidism as in Grave’s disease and hypothyroidism in Hashimoto’s disease, research shows an intensive yoga practice may help to reduce stress and regulate the thyroid-stimulating hormone.^[66] Particular poses and breathing exercises that compress and extend the throat may be most effective, based on these studies’ recommendations. While these findings are speculative, they indicate that yoga may be a safe complementary therapy.

Yoga and Other Disorders

The research on yoga as a medical intervention for a wide range of other disorders, conditions, and capabilities is showing positive results.

HIV or AIDS

For people living with HIV or AIDS (PLWHA), yoga may be a particularly powerful complementary therapy for treating the side effects of antiretroviral medication. Short- and long- term side effects are extensive and are a primary reason patients discontinue treatment.^[67] Most studies show that yoga helps PLWHA manage side effects and symptoms, including chronic pain, stress, substance use, depression, physical inactivity, and blood pressure and also improves quality of life.^[68] A recent review of two such studies, however, found that yoga as a physical activity did not improve functional capacity in terms of strength, cardiovascular fitness, or flexibility of PLWHA.^[69]

There is some evidence that yoga may slow the decline of white blood cells and the progression of HIV by decreasing stress and depression.^[70]

Cancer

Yoga may also be effective for treating cancer symptoms and cancer treatment side effects. There have been a multitude of studies with a variety of methods used to research this topic across a variety of ages, types and states of cancer, and cancer treatments. While it’s impossible to draw firm conclusions, there are positive indications that yoga may be an effective adjunct therapy in cancer treatment by reducing depression, anxiety, and psychological distress.^[71] For breast cancer patients, which a majority of research studies on yoga and cancer have focused on, there is also some evidence that yoga reduces pain, fatigue, sleep disturbances, lymphedema-related swelling in the arms, and treatment-related toxicity.^[72]

There have been few studies on pediatric cancer, but tentative results show a correlation between the practice of yoga and decreased anxiety and increased quality of life and functional mobility in children and adolescents.[73]

Aging

Yoga has also been tested as a treatment for aging-related conditions. As mentioned earlier, in regards to physical health, yoga has particular benefits for the elderly. It has been shown to increase the fitness, strength, balance, and mobility of this population, and yoga is more accessible and lower impact than other types of exercise.

In a study on yoga interventions for patients with Parkinson’s disease, a yoga group had similar results to an exercise group for improved balance and sway, and some evidence suggests that yoga improves tremors and motor function in Parkinson’s patients.^[74] For people with dementia, some studies showed that practicing yoga increased the brain’s grey matter and improved cognitive functioning, in addition to providing other physical and mental health benefits.^[75] For people with the most common form of dementia, Alzheimer’s disease, practicing chair yoga was shown to improve physical functioning in moderate and severe cases.^[76]

Family caregivers of people with dementia may benefit from yoga as well--studies indicate yoga may reduce depression and anxiety, improve cognitive functioning, and positively affect stress-related genetic markers among this population.[77]

Critical Evaluations

There are certainly positive trends in yoga as a medical intervention, but there continue to be research challenges that weaken these findings. These challenges are a result of the field’s rapid growth and diversity. Researchers commonly acknowledge these challenges and note that their work lays the foundation for more robust future studies.

One critical evaluation of yoga intervention studies centers on study design. For example, there have been few long-term studies, few large-scale studies, few large sample size studies, few follow-up studies, and few randomized, controlled trials. Randomized, controlled trials are well respected in the medical community and considered effective in evaluating new treatments, because they minimize bias by randomly assigning study participants to a control group and an experimental group without the participants’ knowledge. While this type of research on yoga is increasing, participants cannot be made “blind” to yoga interventions (they know they are practicing yoga) in the same way participants in other medical studies might be blind to whether they are taking an experimental medication or a placebo.

Another limitation is that many studies measure the success of a yoga intervention by comparing pre- and post-tests on the same group of participants or by comparing a yoga intervention to no intervention. While yoga is often superior to no intervention. when compared to an active intervention such as exercise, yoga is not commonly found to be superior.^[78]

There is also the challenge of yoga intervention definitions and dosages. There is great variety in yoga and a greater need for studies to accurately describe the yoga intervention, including the yoga style (ranging from purely meditative to purely physical) and its length, frequency, and duration. It appears that different yoga styles yield generally the same treatment effects when compared to each other, but meditation and/or breathing-based yoga styles are more effective for reducing depression and asthma symptoms.^[79]

In sum, methodological variety and inadequate study descriptions complicate efforts to confidently draw conclusions about yoga interventions. Nonetheless, as seen in other areas of medical research, the quality of yoga intervention research has improved over time. Since the Consolidated Standards of Reporting Trials (CONSORT) guidelines were released in 2001, reporting of study parameters has improved, but many yoga research studies still fail to report adequate randomization and have unclear or a high risk of selection bias. The trend continues outside the United States where randomized, controlled trials (particularly those from India) tend to be published in complementary and alternative medicine specialty journals or published in journals without or with low impact factors, which are more likely to be biased towards positive results.[80] Risk of bias correlates most strongly with publication year and journal impact factor, with more recent studies published in higher impact factor journals having less risk of bias.^[81] This mirrors the larger trend in emergent research fields, that the quality of the research and its reporting improves with time. It may also be that standard CONSORT guidelines are not comprehensive enough for yoga intervention research and that further yoga-specific research and publishing guidelines would improve research quality.^[82]

Research on yoga interventions will also improve with increased attention to safety and the reporting of adverse events. Yoga interventions appear to be as safe as usual care or exercise, with few adverse events from any type, but less than one third of all published studies on yoga interventions include sufficient safety reporting.^[83] Physically demanding yoga styles such as ashtanga and heated yoga styles such as Bikram have more adverse events, and adverse events are more likely when performing advanced poses such as head stands, shoulder stands, and lotus poses and when engaged in intense yogic breathing exercises, such as kapalabhati.^[84] People with recent abdominal surgeries, lung, or respiratory conditions should be careful with all intense yogic breathing exercises; people with glaucoma should avoid inversion poses; and people with bipolar disorder and trauma conditions should be aware that some poses may trigger or aggravate their conditions.^[85] There is also increased risk of adverse events from yoga for the elderly and people with chronic conditions.^[86] Overall, yoga can safely be recommended as an adjunct treatment, but it should be adapted and practiced with caution by vulnerable populations.

Future Research

A critical evaluation of yoga intervention studies makes clear that future research requires more rigorous methods and reporting, including better randomization, lower risk of bias, more control and comparison groups, longer follow-up periods, larger sample sizes, adequately described interventions and dosages, and improved safety reporting. Such improvements will also aid researchers in comparing styles of yoga, comparing yoga to similar exercise, comparing yoga to other contemplative or mindfulness practices, and deepening investigation into the mechanisms of effective yoga interventions. Yoga’s efficacy is explained in part by its correlation with decreasing stress and unhealthy inflammation; increasing strength, flexibility, and body awareness; and balancing of hormone and cortisol levels. However, more work is necessary to understand the biologic and physiologic causes of these effects. For example, there is some evidence that a yogic lifestyle leads to lengthened telomeres, which are associated with healthy aging and longevity.^[87]

Additionally, future research must expand beyond adults with medical conditions to include children, adolescents, and healthy participants as well. Recent efforts in this regard are already promising. There is a growing research trend to study how yoga can be used in schools to help students manage stress and behavior for academic success. One study speculates that giving young people these mind-body skills will limit stress for them in the future, even as adults.^[88]

Research must also continue to expand to consider a wider range of conditions. For example, most cancer research on yoga interventions focuses specifically on breast cancer, and most autoimmune disorder research on yoga interventions focuses specifically on MS. This research has established relevance and purpose for widening the scope of study to include other cancer types and autoimmune disorders.

Future research should also more closely examine barriers to yoga interventions. Yoga interventions are praised as holistic, natural, and without side effects. This is true, but there are challenges to behavior-based interventions such as yoga, including time constraints, cost, transportation, and childcare. Even practicing yoga at home requires space and limited distractions. Cost-effectiveness is another important concern. One study found health insurance in the United Kingdom covered some yoga interventions for a limited number of conditions, with health insurance in the United States covering fewer yoga interventions on average.^[89] In the United States, barriers to yoga interventions may also include cultural perceptions of yoga as an activity for white women. This is exacerbated by the fact that white women comprise the majority of study participants—a trend that will continue unless study designers intentionally target other populations.

Conclusions and Implications

Though confirming empirical evidence remains tentative, yoga is found to be a feasible, practical, low-risk intervention as a preventative measure and a complementary treatment for many conditions. While the elderly and those with chronic conditions should take care in beginning a yoga practice, yoga offers an adaptable low-impact alternative to exercise. Increased communication and open conversations among patients, doctors, and yoga instructors about goals, conditions, and concerns will lead to more positive and effective yoga interventions.

Research on yoga interventions is becoming more expansive and rigorous over time with increasing publication of randomized, controlled trials in peer-reviewed, high-impact journals. Future research will include broader demographics and a wider range of target populations, a greater variety of conditions and diseases, and a deeper consideration of barriers.

Yet, additional attention is needed to strengthen current findings, and rapid growth in this research field and the diversity of yoga styles will continue to present methodological and reporting challenges. While these challenges mirror “growing pains” in other medical fields, yoga research may have distinct challenges that require innovative solutions.

Side Bar – Yoga Styles

Hatha yoga is traditionally a category of yoga styles that focus on poses; the term now also denotes a gentle yoga style that is slow-moving with each pose held for a few breaths.

Vinyasa yoga is a dynamic flow style that links movement and breath, raising the heart rate.

Iyengar yoga is an anatomy-focused style that uses props, blocks, and straps to create alignment.

Ashtanga yoga is a self-paced sequenced style that requires one pose to be mastered before moving onto the next pose.

Hot yoga is done in a heated room. One style of hot yoga is Bikram yoga, which is always the same poses done in the same order.

Kundalini yoga is an energy-based style that combines repetitive movement with breath, chanting, and meditation.

Yin yoga and restorative yoga are similar relaxation styles that use bolsters, blocks, and blankets to release tension in long holds.

Prenatal yoga is a style for pregnant women that focuses on preparing for labor and delivery through pelvic floor work, breathing, and bonding with the baby.

New yoga styles are emerging all the time, including anusara yoga, Forrest yoga, Jivamukti yoga, Power yoga, and Buti yoga.

Yoga hybrid styles are increasingly popular, such as pilates-yoga (PiYo), acrobatics-yoga (AcroYoga), weight-lifting-yoga (Yoga Sculpt), Stand-Up-Paddleboard-yoga, and a wide range of animal-themed yoga classes, where cats, dogs, goats, sloths, etc. may be present.