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Evaluate the evidence for clinical applications of yoga among the pediatric population.
We conducted an electronic literature search including CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Medline, PsycINFO, and manual search of retrieved articles from inception of database until December 2008. Randomized controlled trials (RCTs) and non-randomized controlled trials (NRCTs) were selected including yoga or yoga-based interventions for individuals aged from 0 to 21 years of age. Data were extracted and articles critically reviewed utilizing a modified Jadad score and descriptive methodological criteria with summarization in tables.
Thirty four controlled studies were identified published from 1979 to 2008, with 19 RCTS and 15 NRCTs. Many studies were of low methodological quality. Clinical areas for which yoga has been studied include physical fitness, cardio-respiratory effects, motor skills/strength, mental health and psychological disorders, behavior and development, irritable bowel syndrome, and birth outcomes following prenatal yoga. No adverse events were reported in trials reviewed. While a large majority of studies were positive, methodological limitations such as randomization methods, withdrawal/dropouts, and details of yoga intervention preclude conclusive evidence.
There are limited data on the clinical applications of yoga among the pediatric population. Most published controlled trials were suggestive of benefit, but results are preliminary based on low quantity and quality of trials. Further research of yoga for children utilizing a higher standard of methodology and reporting is warranted.
Yoga is a mind-body practice that originated in India at least 2000 years ago. For over two millennia, yoga has evolved into different schools of thought, while maintaining the purpose of directing the mind and body. There are common elements to many forms of yoga which may include some or all of the following: postures (asanas), breathing (pranayama), and meditation. In 2007, there were over 1.5 million pediatric yoga users in the U.S.1 Within popular culture, yoga is perceived as a way to develop and maintain a healthy mind and body, and is commonly taught in health gyms, spas, schools and colleges and featured in wellness magazines.
Recently, there has been increasing interest and research in the therapeutic applications of yoga to prevent or treat medical conditions.2 Epidemiological research among adults suggests that many individuals use yoga for health maintenance and perceive benefit for overall health, musculoskeletal and mental health conditions.3 Clinical trials with adults suggest potential benefit for various conditions including back pain,4–7 osteoarthritis,8, 9 cardiovascular disease,10, 11 and depression.12–14 In contrast, very little is known about the safety and efficacy of yoga among the pediatric population. A systematic review performed by Galantino and colleagues in 2008 identified 24 studies of yoga for children including case-control studies, pilot studies, cohort studies and randomized controlled trials (RCTs) that focused on studies of relevance to physical therapy.15 The review concluded that there was evidence for the benefit of yoga in the pediatric population in rehabilitation, but more research is necessary. This study selected and categorized articles most relevant to physical therapy practice, however may have excluded articles of interest to general pediatrics. The purpose of this systematic review is to identify evidence for applications of yoga for all pediatric conditions. Also, we critically reviewed the methodological quality among selected studies to help inform future research in this field.
We systematically searched multiple databases including CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Medline, and PsycINFO. We utilized the MeSH terms infant, child, adolescent, pediatric and coupled each with yoga to perform a search from inception of database until December 2008. Additionally, we searched the bibliographies of obtained yoga articles for additional publications that would meet our criteria.
We included randomized and non-randomized controlled trials (NRCTs) with subjects in the age range of 0 to 21 years. Trials that combined results with individuals older than 21 years were excluded. Studies were included if they specifically stated that the intervention was yoga or yoga-based exercise. Yoga interventions that incorporated non-yoga modalities (e.g. games, massage, interactive discourse, non-specified relaxation techniques) were included as well. Dissertations, abstracts, and non-English publications were excluded. We also excluded studies that reported meditation in the absence of specifically stating yoga, and excluded studies utilizing mindfulness-based stress reduction, transcendental meditation, or relaxation response.
Data were extracted systematically by two of the authors independently. Among those studies that met our criteria, we collected data on: study population, yoga intervention, non-yoga co-interventions, control or comparison groups, methodology, outcome measures, and adverse events. Age categories were organized as neonate (0–1month), infant (1 < to 24 months), young child (2 < to 5 years), older child (5 < to 12 years), adolescent (12 < to 18 years), and young adult (18 < to 21 years).
To evaluate the quality of reporting, we used a modified Jadad Score for randomized controlled studies (RCTs). The Jadad Score, a well validated instrument, measures the quality of reporting with a numerical scoring system from 0 to 5 (0 being weak and 5 being strong).16, 17 Values are assigned based on the adequacy of reporting methods including randomization, double blinding, and withdrawals/dropouts. The modification of the Jadad Score we utilized allows one point for single blinding (i.e. in the case of yoga, outcome assessor blinded), rather than two points for appropriate double blinding which is difficult to employ in yoga studies. To further describe the methodological quality of the RCTs, we used a method previously reported 18 to collect the following information (Yes/No): randomization method described, outcome assessor blinded, withdrawal/drop outs reported, sample size justification, intention-to-treat analysis, appropriate data analysis, adequate description of yoga intervention, adequate description and justification for control group, and description of yoga instructor’s qualifications. A second investigator evaluated 20% of the final selected RCTs and we calculated a kappa coefficient for agreement to assess the reliability of our data collection methods. We obtained a kappa score of r = 1.0, suggesting excellent reliability.
Figure 1 portrays the flow of our search and selection process. Our initial search of the databases resulted in a total of 351 studies. We screened and excluded articles that were not yoga or yoga-based (127), were adult only or combined data from adults with children (80), not trials (53), lacked a control group (22), non-English (19), dissertations (7), duplicated publications (5), and abstracts (4). We identified 34 studies that met our inclusion criteria which are detailed in Table I organized by medical condition/category (19 RCTs and 15 NRCTs). A large majority of studies were conducted in India (21), followed by United States (9), Australia (2), Canada (1), and Germany (1). We identified 26 studies of children less than 18 years as follows: 11 adolescent, 10 older children, 3 combining adolescent and older children, 1 neonate, and 1 unspecified age. There were no studies of younger children (2–5 years). The pediatric populations studied included healthy, normal children (11), attention deficit and hyperactivity disorder (2), educational problems (2), domestic/social problems (2), fitness failures (1), irritable bowel syndrome (1), depression/adjustment disorder (1), examination anxiety (1), poor motor coordination/low body satisfaction (1), eating disorder (1), impaired vision (1), mental retardation (1), and prenatal/newborn (1). There were 8 studies of young adults (18–21 years), all of whom were healthy normal subjects. Studies varied in the yoga techniques and c o-interventions utilized as shown in Table II. Many studies used common yoga techniques such as: postures (79%), breathing (67%), and/or meditation (59%). While still considered a posture, the corpse pose (shavasana), was categorized separately due to the high frequency of use in studies individually or alongside other yoga interventions (26%). Nearly 1/3rd of the interventions included other yoga techniques such as: locks (bandhas), cleansing exercises (kriyas), hand gestures (mudras), lectures on yoga philosophy, yoga diet, and devotional songs. The duration of the interventions varied from a single day to an entire year, with an average length of 9 weeks. Longer studies and those that used techniques other than postures, breathing, and meditation were more commonly conducted in India. No adverse events were reported in any of the studies reviewed.
We report the modified Jadad scores of RCTs in Table I. Generally, the RCTs had low modified Jadad scores with few studies receiving a score of 3/5 (2 studies) or 2/5 (4 studies), and a large majority received 1/5 (13 studies), highlighting the poor quality of reporting in these studies. In Table III, we also analyzed the methodological quality of the 19 RCTs. Among 19 RCTs identified, 2 reported the method of randomization,19, 20 1 reported single blinding of outcome assessor,20 and 4 reported withdrawals/dropouts.19, 21–23 None of the RCTs provided sample size justification or an intention-to-treat analysis. Only 12 studies provided details of the yoga intervention, and most lacked information on the qualifications of the yoga instructor. Many of the studies lacked an appropriate data analysis (11/19 RCTs). The most common statistical error was not measuring changes in the intervention group as compared to the control group. Many studies reported significant changes based on differences from pre-intervention to post-intervention for the yoga group and control group separately (within-group analysis).24–33
Yoga was studied as a means to physical fitness in India by Moorthy et al for children who had failed a fitness test (Table I-A1).31 While this study reported only within-group analyses, results suggested that yoga increased the number of children that were able to pass the fitness test. The study included a third arm with physical activity, which showed no difference in percentage that passed the fitness test in comparison to yoga. In a RCT, using a comprehensive yoga intervention, including dietary modification and philosophy, compared to regular activity, Bera and colleagues reported higher cardiovascular fitness and increased lean body mass among subjects in the yoga group after one year.34 Given the multi-modal intervention, it is unclear if the changes in lean body mass were due to diet changes alone. Statistical analysis was also measured as within group pre/post change rather than between group comparisons of intervention and control.
With regards to cardiovascular effects, studies seem to suggest that yoga lowers blood pressure, heart rate, and respiratory rate in children and young adults (Table I-A2). Bagga et al demonstrated that corpse pose practiced regularly for 12 weeks by young adult women may reduce systolic blood pressure as compared to regular activity.35 Other pediatric yoga RCTs also reported changes comparing pre/post within group changes in cardiovascular and respiratory parameters: decreased blood pressure response to cold pressor test (a cardiovascular test conducted by immersing one hand of subject in cold water and measuring changes in blood pressure and heart rate) among young adults who at baseline had hyper-reaction to cold pressor test,25 improved respiratory capacity in normal adolescents, 27 decreased heart rate and respiratory rate in adolescent girls with domestic social problems,32 and decreased respiratory rate in adolescents with vision impairment.33
We identified 5 studies whose outcomes measured motor skills or strength (Table I-A3). Outcomes included balance,36 fine motor skills,37 and hand grip strength38, 39 but these studies were of low quality based on quality of reporting.
Yoga has been studied to enhance the mental health of children (Table I-B1). For example, a single session of yoga prior to a long distance run in high school athletes improved performance of a one mile run as compared to a normal routine group. The yoga intervention was to mentally and physically prepare the runners for the one mile run. However, there was statistically less improvement in comparison to a motivational group. Two NRCTs examined yoga’s impact on mood among healthy young adult students.40, 41 Both studies lacked a detailed description of the yoga intervention. These studies suggested a benefit of yoga, as well as physical activity, on mood by reducing stress and negative emotions. Berger and colleagues identified gender differences in outcome, with decreased tension, anger and fatigue among males who received the yoga intervention in comparison to swimming. West et al reported cortisol increasing among the African dance group and decreasing among the yoga group with a significant difference between groups.
A single RCT exists for the therapeutic application of yoga, as compared to a dissonance-based intervention, or control group to treat young adult women with eating disorders (Table I-B2).22 While overall, this study was well designed, the yoga intervention is minimal (once a week for 45 minutes) and not well detailed. The dissonance intervention showed benefit on multiple outcomes in comparison to the control, while the yoga intervention had no difference compared to the control. A NRCT studied normal girls and the effects of multimodal intervention including yoga on measures that predict future risks of eating disorders.42 The intervention group showed positive changes in some, but not all outcomes measured. Since the intervention group contained other modalities, the role of yoga is uncertain.
Two other NRCTs studied the effects of a relaxation intervention on the mood of inpatients with depression/adjustment disorder 43 and students with abnormal examination anxiety (Table I-B3).44 While suggestive of benefit, these studies combined yoga with other relaxation modalities, which limits interpretation of the role of yoga in observed outcomes.
There have been a small number of studies utilizing yoga with children that have behavioral or developmental problems (Table I-C). We identified two studies of the use of yoga for the management of attention-deficit hyperactivity disorder (ADHD) (Table I-C1).21, 45 These two studies were limited by low adherence and small sample sizes. Comparison of the trials is difficult, since Jenson et al utilized a yoga intervention composed of meditation, breathing, and postures for children, while Harrison et al utilized Sahaja yoga, a family meditative intervention. The results of these studies were mixed, but suggested a potential benefit of yoga for ADHD symptoms. A third NRCT studied yoga for elementary children with a non-specific diagnosis of “attention problems in school”, which was intended to encompass children with ADHD.46 This study demonstrated increased attention from pre/post yoga intervention, but did not compare changes to the control group. Another controlled trial lacking detail of the subject population was reported by Hopkins et al in 1976 utilizing yoga for elementary children vaguely categorized with “educational problems”.47 There was one study examining the affect of yoga on elementary and adolescent children with mental retardation. While the study reported improvement in Intelligence Quotient (IQ) and social adaptation in the yoga group compared to the control group (Table I-C4),23 the study calculated outcome changes incorrectly (difference between yoga and control group measurements at baseline compared to difference between yoga and control group measurements post-intervention). Based on the quality of the study, there is no evidence that yoga can improve IQ.
Many studies from India have explored how yoga may influence visual and cognitive skills in children (Table I-C2, C3 respectively). These studies include changes in verbal and spatial memory,48, 49 visual perception,20, 29, 39 and executive function.30 Generally, all these studies reported a benefit of yoga in the capacities listed, however poor methodology precludes conclusive evidence.
A RCT from 2006 with adolescents that had irritable bowel syndrome, randomized subjects to yoga or wait-list control (Table I-D).19 The yoga group as compared to the control group had decreased functional disability, emotional-focused avoidance, and anxiety. The investigators combined the data from the yoga group with the wait list group after these subjects completed the intervention, and reported a pre/post reduction in gastrointestinal symptoms.
We identified 26 controlled studies of yoga for the pediatric and 9 for the young adult population. The methodological quality of many studies was low. Areas for which yoga has been studied include physical fitness, cardio-respiratory effects, mental health, behavior and development, irritable bowel syndrome, eating disorders, and prenatal effects on birth outcomes. A large majority of the studies were positive, but due to methodological limitations the evidence provided is preliminary at best.
Our review differs from the recent systematic review of yoga for children published by Galantino et al. These authors used search terms related to yoga, pediatrics (children, developmental disabilities), exercise, and publication types that were of interest. Studies were included with primary outcomes of quality of life, cardio-respiratory fitness, and physical functioning or with secondary outcomes of attention and cognition. The review categorized studies based on relevance to physical therapy into three domains: neuromuscular, cardiopulmonary, and musculoskeletal headings. Whereas we identified 34 studies including NRCTs and RCTs, the Galantino review identified 24 studies including cohort, case-control, and RCTs. Among the 34 trials included in our review, 18 studies (11 RCTs and 7 NRCTs) are unique to our study and are not reported by Galantino.19, 20, 22, 24, 25, 29, 31, 34–36, 40–42, 47, 50–53 Our study reviewed 16 studies also in the Galantino review,21, 23, 26, 27, 30, 32, 33, 37–39, 43–46, 48, 49 with the remaining 8 studies excluded here based on our exclusion criteria as follows: age,54–57 no control group,58–60 and not a trial.61 The differences in our review may have stemmed from contrasting search strategies including: different search terms (e.g. infant, adolescent), our specific age inclusion criteria (0 to 21 years), and our inclusion of all outcomes (not only quality of life, attention, and cognition).
Preliminary evidence presented in this review suggests that yoga may be beneficial for physical fitness and cardio-respiratory health among children. As a physical form of exercise, studies suggest that yoga provides low aerobic intensity.62, 63 According to the 2002 NHIS, a large majority of adults who use yoga in the U.S. reported that yoga was important for their health maintenance.3 Based on our review, yoga may be an option for children to increase physical activity and fitness. In particular, yoga may be a gateway for adopting a healthy active lifestyle for sedentary children who are intimidated by more vigorous forms of exercise. However, studies have been predominately conducted in India, where yoga is culturally more acceptable and adaptable.64 Studies in different cultural settings are necessary to better evaluate the feasibility of yoga as a form of exercise for children.
More studies outside of India have explored the use of yoga for psychological health. This research focus is consistent with a national survey among adults in the U.S., where yoga users were more likely to have mental health conditions, and mental health was one of the most common conditions yoga was used to treat.3 A systematic review by Pilkington in 2005 found yoga may be beneficial for adults with depression. We identified two NRCTs that suggested yoga, as well as conventional exercise (swimming or dance), promoted mental health. However these studies were among young adults, and have to be replicated for individuals less than 18 years old.
As a means of developing mental and physical discipline and self-awareness, yoga intuitively would have possible benefit for children with ADHD. However, to date initial studies show potential, but are far from conclusive. In general, the clinical applications of yoga for pediatric behavior and development have yet to be determined.
Prenatal yoga has become increasingly popular in mainstream culture in the U.S., but surprisingly, we found only one study from India that measured health outcomes on neonates. While a positive NRCT, this study needs to be followed by more rigorous research to evaluate the application of yoga for this population.
Our review suggests need for improved methodology and reporting of yoga studies in children. Many RCTs did not describe randomization methods. None of the studies provided sample size calculations, and many had small sample sizes. These studies may not have sufficient power to measure changes in reported outcomes. In addition, inappropriate statistical analysis of within group pre/post changes rather than between group comparisons undermines the principle of conducting an RCT. Studies need to explain the rationale of the control groups, including why the control group is an appropriate comparison to the yoga intervention group. Most studies did not report withdrawals/dropouts, which is necessary to determine feasibility and adherence to the protocol, along with an intention-to-treat analysis. None of the 34 studies reported adverse events or lack thereof. This may suggest that yoga is a low risk intervention among children. However, since this was not specifically reported in these trials, it also may represent underreporting of adverse events. The risks of yoga have not been well documented with some case reports in the literature.65–73 Future prospective controlled studies should collect data on adverse events.
Yoga represents a myriad of practices, and we found that studies lacked adequate description of the yoga interventions. Without detailed description of the specific techniques used, comparison and replication of studies to validate results are difficult. Also, the qualifications of yoga instructor(s) need to be clearly stated due to variations in style and experience. Registration of yoga teachers with national standards of yoga training, such as the minimum of 200 training hours recognized by the Yoga Alliance (www.yogaalliance.org), will help standardize yoga interventions. However, these standards apply to training yoga instructors to teach adults, while no standards exist for instructors teaching children. Specific training and experience teaching yoga to children should be described.
There are limitations to our study including the low number of publications, especially for any given outcome. This precludes further analysis with quantitative methods such as meta-analysis for specific outcomes. The variability of yoga interventions and the lack of detail in yoga description make comparison and interpretation of these studies difficult. Studies spanned a broad age range, and yoga for different age groups is difficult to compare based on varying developmental age and medical conditions. Yoga very likely has different effects and feasibility among different age groups. Based on experienced yoga teachers, younger children are often taught yoga that emphasizes physical exertion with many dynamic postures, and less breathing and meditation. As children grow older, more breathing and meditation are incorporated. This reflects the developmental stage of the child to allow them to be engaged and focused in the practice. This systematic review does not provide sufficient data to identify particular patterns of yoga for specific populations and settings. We excluded studies with mixed populations of children and adults. Generally, studies among all age groups were positive, however publication bias cannot be ruled out in this descriptive systematic review. We also excluded studies that were not controlled, and these studies may have contributed some valuable information. However, the absence of control groups in trials, particularly behavioral trials, make any result highly suspect with placebo effects and other sources of confounding. Studies published in languages other than English were excluded, which may have caused language bias. Our definition of yoga was narrow, and excluded practices that contain similar or co-opted relaxation techniques. For example, mindfulness-based stress reduction commonly incorporates some aspects of yoga in the intervention. For reasons of practicality, we limited our study to interventions that were clearly described as yoga or yoga-based. Despite these limitations, our systematic review describes the state of research for yoga in children, and can help direct future investigations.
As yoga continues to gain in popularity among children as a recreational activity or a behavioral therapy, there are a wide variety of traditions and styles. These variations are not clearly delineated by age. Although there is a growing body of literature, the existing methodology is very poor. Thus, it is difficult to comment on the clinical efficacy. The trials did not report adverse events, suggesting that yoga has a high safety profile. Further research is necessary to identify clinical applications of yoga for children. As a mind-body modality, applications in pediatric mental health and physical fitness need to be studied. Research on the use of yoga for disorders of behavior and development, such as ADHD, need to be developed. Research needs to be conducted with rigorous methodology in RCTs with detailed description of protocols and reporting of results. RCTs of yoga should utilize guidelines established by the Consolidated Standards of Reporting Trials (CONSORT) group for the reporting of trials.74 In addition, methodological issues specific to mind-body interventions should be addressed including adequate description of the intervention and control group, and single blinding of the outcome assessor. Evidence-based prescription of mind-body techniques, such as yoga, for overall health maintenance or for specific diseases in children will depend on the development of this research agenda.
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