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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