The Harvard community’s Research on Yoga and Health: An Awareness Approach


Introduction:
The conceptual background of yoga has its origins in ancient Indian philosophy. There are numerous modern schools or types of yoga (i.e., Iyengar, Viniyoga, Sivananda, etc.), each having its own distinct emphasis regarding the relative content of physical postures and exercises (asanas), breathing techniques (pranayama), deep relaxation, and meditation practices that cultivate awareness and ultimately more profound states of consciousness. The application of yoga as a therapeutic intervention, which began early in the twentieth
century, takes advantage of the various psycho physiological benefits of the component practices. The physical
exercises (asanas) may increase patient’s physical flexibility, addressed were psychiatric, cardiovascular, and respiratory disorders [3]. Despite a growing body of clinical research studies and some systematic reviews on the therapeutic effects of yoga, there is still a lack of solid evidence regarding its clinical relevance for many symptoms and medical conditions. For many specific indications and conditions, there is inconsistent evidence with several studies reporting positive effects of the yoga interventions, but other studies are less conclusive.
In some instances, these discrepancies may result from differences between the study populations (e.g., age, gender, and health status), the details of the yoga interventions, and follow-up rates. In this paper,  The researchers of Havard University summarize the current evidence on the clinical effects of yoga interventions on various components of mental and physical health. In general, the respective reviews (Table 1) and an Agency for Healthcare Research and Quality Report (AHRQ) evidence report on “Meditation Practices for Health,” which cites also studies on yoga [30], include a heterogeneous set of studies with varying effect sizes, heterogeneous diagnoses and outcome variables, often limited methodological quality, small sample sizes, varying control interventions, different yoga styles, and strongly divergent duration of interventions.

Depression.  The researchers of Havard University found four relevant publications, including two reviews on the effects of yoga on depression[4, 5],  a description of studies on yogic breathing [6] for depression, and one “summary” [8]. The reviewing authors have reported that the studies reviewed showed a large variety of diagnoses ranging from “major depression or some other type of diagnosed depression” to “elevated depressive symptoms” . Although several randomized controlled trials (RCTs) reported beneficial effects of yoga interventions for treating depressive symptoms, the quality and quantity of the data from these studies appear insufficient to conclude whether there is substantial clinical justification to consider yoga as a treatment of depression. Compared to passive controls, the yoga interventions seem to be effective; when compared with active controls, not surprisingly, the effects are less conclusive [5]. The study results are so far not sufficient in quantity and quality to determine whether studies with a focus on the asanas are more effective as compared to studies with meditation-focussed or pranayama-focussed styles. Thus, there is a strong need to conduct more conclusive studies with high methodological quality and larger patient samples. Whether motivation of depressed patients could be a problem or not remains to be clarified. There has been an attempt to explore mechanisms of action and to understand the complete picture of the effects of yoga in depression looking at electrophysiological markers of attention, and neurotransmitters which were found to change with yoga.

 Fatigue.  The researchers of Havard University found one systematic review/meta-analysis evaluating the effects of yoga on fatigue in a variety of medical conditions. The review included 19 RCTs and includedto standard drugs. However, there are currently no metaanalyses available which would clearly differentiate this important issue. At least the AHRQ report stated that “yoga was no better than Mindfulness-based Stress Reduction at reducing anxiety in patients with cardiovascular diseases

Stress. One systematic review describes the effects of yoga on stress-associated symptoms. Chong et al. identified 8 controlled trials, 4 of which were randomized, which fulfilled their selection criteria [11].Most studies described beneficial effects of yoga interventions. Although not all studies used adequate and/or consistent instruments to measure stress, they nevertheless indicate that yoga may reduce perceived stress as effective as other active control interventions such as relaxation, cognitive behavioural therapy, or dance.
Also the AHRQ report stated that “yoga helped reduce stress” [30].

Posttraumatic  Stress Disorder. A single review article looked at the existing research on yoga for posttraumatic stress disorder (PTSD) [12]. Seven articles were reviewed which included 8 studies on PTSD following exposure to natural disasters such as a tsunami and a hurricane (1 RCT, 1 NRCT, 3 group study, 2 single-arm studies, 1 cross-sectional study) and 2 studies on PTSD due to combat and terrorism (1 RCT, 1 single-arm study). After a natural disaster, yoga practice was reported to significantly reduce symptoms of PTSD, self-rated symptoms of stress (fear, anxiety, disturbed sleep, and sadness) and respiration rate. Similarly, yoga interventions were able to improve the symptoms of PTSD in persons with PTSD after exposure to combat and terrorism. The interventions varied in duration from one week (when interventions were given on the site) to six months. There view suggested a possible role of yoga in managing PTSD, though long-term studies conducted with greater rigor areneeded [12].

Physical  Fitness. There was one critical review which evaluated whether yoga can engender fitness in older adults [13]. Ten studies with 544 participants (mean age 69.9±6.3) were included; 5 of these studies were RCTs, and 5 studies had a single-arm pre/post-design. With respect to physical fitness and function, the studies reported moderate effect sizes for gait, balance, body flexibility, body strength, and weight loss [13]. However, there is still a need for additional research trials with adequate control interventions (active and specific) to verify these promising findings. One may expect that retaining physical fitness and improving physical functioning can have a positive effect on functional abilities and self-autonomy in older adults. Further studies should address whether or not individuals’ self esteem and self-confidence will increase during the courses, and whether or not regular classes may also improve social

Sympathetic/Parasympathetic Activation.

There were 42 studies on the yoga effects on sympathetic/parasympathetic activation and cardiovagal function [14], that is, 9 RCTs, 16 non-RCTs, 15 uncontrolled trials, and 2 cross-sectional trials. Most studies offered “some evidence that yoga promotes a reduction in sympathetic activation, enhancement of cardiovagal function, and a shift in autonomic nervous system balance from primarily sympathetic to parasympathetic” [14].However, some of the studies included in the review showedless clear-cut or even contrasting, effects. Because most of these effects are short-term phenomena, more rigorous work is needed. Another lacuna is that there are very few studies which have studied plasma catecholamine levels and most of them are early studies [33, 34]. 3.3. Cardiovascular Endurance. Raub’s literature review, which included 7 controlled studies, reported “significant improvements in overall cardiovascular endurance of young subjects who were given varying periods of yoga training (monthsto years)” [15]. Outcome measures included oxygen consumption, work output, anaerobic threshold, and blood lactate during exercise testing. As expected, physical fitness increased in adolescents or young adults (athletes and untrained individuals) compared to other forms of exercise, with a longer duration of yoga practice resulted in better cardiopulmonary endurance.

Yoga and Cardiopulmonary Conditions

Blood Pressure and Hypertension. Innes et al. reported on 37 studies investigating the effects of yoga on blood pressure and hypertension, among them 12 RCTs, 12 nonrandomized clinical trials, 11 uncontrolled studies, 1 cross-sectional study, and 1 single yoga session examination. Most reported a reduction of systolic and/or diastolic pressure. However, there were several noted potential biases in the studies reviewed (i.e., confounding by lifestyle or other factors) and limitations in several of the studies which makes it “difficult to detect an effect specific to yoga” [14
Pulmonary Function. In his descriptive literature review, Raub also examined studies evaluating yoga’s effects on lung function in healthy volunteers and patients with chronic bronchitis and asthma [15]. In healthy volunteers practicing yoga, there are reported improvements of various parameters of lung function with breathing control techniques, specific postures, and/or relaxation techniques [15]. However, these
improvements were “not consistent and depended upon the length of yoga training, the type of yoga practice used (e.g., breathing exercises and yoga postures), and the type of subject” [15]. Raub also cited some studies on patients with asthma describing improvements in peak expiratory flow rate, medication use and asthma attack frequency. In a double-blinded RCT with placebo-control, [35] there were only a few small and insignificant improvements in lung function variables. Thus, more rigorous trials are needed to clarify the value of yoga breathing practices for patients with asthma.
5. Yoga andMetabolic/Endocrine Conditions

Glucose  Regulation. Three systematic reviews examined the effects of yoga on risk indices associated with insulin resistance syndrome [14], risk profiles in adults with type 2 diabetes mellitus [16], and the management of type 2 diabetes mellitus [17]. Innes et al. [14] identified several studies on the effects of yoga on insulin resistance syndromeassociated variables, that is, 2 RCTs, 2 non-RCTs, and 8 uncontrolled clinical trials. These studies reported postintervention improvement in various indices in adults. However, the results varied by population (healthy adults, adults at cardiovascular disease risk, adults with type 2 diabetes, etc.) and study design. Another systematic review by Aljasir et al. [17] addressed the management of type 2 diabetes mellitus and concluded that the reviewed trials “suggest favourable effects of yoga on short-term parameters related to diabetes but not necessarily for the long-term outcomes.” However, the duration of treatment in the reviewed studies was variable (ranging from 20 min. session per day to three to five 90min. sessions in the review of Aljasir et al. [17]; 3-4h per day for 8 days, 2 sessions per day (25–35 min) for 3 months to 40 min per day for 6 months, and 72 4 h sessions during 12 months in the review by Innes and Vincent [16]). The AHRQ cites two studies comparing yoga versus medication which reported a large and significant reduction of fasting glucose in individuals with type 2 diabetes in one study, and a smaller but still significant improvement in the other study [30]. The authors discussed differences in the study populations, and interventions as possible explanation for the observed heterogeneity of results.
5.2. Menopausal Symptoms. A single review addressed
Menopausal symptoms and analyzed 3 RCT, 1 N-RCT, and 3 uncontrolled clinical trials [18]. Although some studies reported beneficial effects, “the evidence was insufficient to suggest that yoga is an effective intervention for menopause”[18].

Conclusion:

 It is acceptable, accessible and cost-effective that Yoga encourages self-reliance. Yoga is an individual health promoting practice but can be done in groups and supported by communities. Like other holistic practices such as tai chi, qigong, meditation and so forth, it includes a community component. Practicing yoga together, in workplaces, schools and other group settings have shown to promote mental health [24]. While yoga does not address the social determinants of mental illness it does promote a greater sense of inner peace for those who parctise. It appears that deep slow breathing in combination with movement and other aspects of yoga are at the heart of yoga’s ability to bring people a greater sense of tranquillity. It meets the triple aim of improving health, improving care and reducing cost. A recent article questions whether sufficient evidence exists for family physicians to recommend yoga to their patients. The evidence-based answer: “Yes, yoga can reduce symptoms of anxiety and depression (strength of recommendation [SOR]: B, systematic reviews of randomized controlled trials [RCTs] with significant heterogeneity). Across multiple RCTs using varied yoga interventions and diverse study populations.  Yoga typically improves overall symptom scores for anxiety and depression by about 40%, both by itself and as an adjunctive treatment. It produces no reported harmful side effects.” In some cases yoga is taught for free such as yoga clubs in India and other countries. While it may not be for everyone, through a disciplined approach most people with or without mental health imbalances may feel more mental ease and relaxation through the practice of yoga.
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