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Table 1. Inclusion and exclusion criteria used when selecting articles in the systematic review

Inclusion criteria Exclusion criteria
Population People above 18 years old People with clinical symptoms (physical or mental disorder, or undergoing regular
medical check) or in shift-work schedule
Intervention/exposure Yoga based study on stress Review (systematic review; meta-analysis)
Empirical or observational longitudinal study (follow-up study or retrospective study); Mixed study methods
Original studies
Comparison Contain intervention and controlled Case-control studies
groups
Outcome Outcome elaborated the effect of yoga on stress
Other Timeframe from January 2014 to Questionable analysis methods.
November 2018 Non-English study

increasing cardiac output, which inherently influence basal P (population): Regular healthy participants (not
metabolic rate. As to cognitive function, yoga practice hospitalized patients or with clinical diseases, not
5
showed no significant improvement in healthy population; pregnant ladies, not in day-night shifting works).
however, yoga practice disclosed inspiring results in quality I (intervention/exposure): Organizing yoga-based
of life and physical measures. Nevertheless, yoga-based intervention.
6
intervention program is feasible and efficacious in creating C (comparison): Studies comparing healthy adults
positive improvements of health and wellness. 7 conducting yoga practice versus healthy adults not
The psychological effect of yoga has been examined in conduction yoga practice, where such comparison
previous study. Yoga appears to work on depression, anxiety, has been performed;
and self-efficacy. For instance, a systematic review carried out O (outcome): Effects of yoga practice on stress.
in 2004 investigated the effectiveness of yoga on the treatment
of anxiety and anxiety disorders. Evidence reported Inclusion and Exclusion Criteria
encouraging results with obsessive compulsive disorder The source of stress differs in adults regarding to the life
despite the diversity of intervention conditions and deficient management and social engagement. We accepted only
quality of the studies. Demonstrated by a recent review that studies conducted within adults (18 years and older in this
8
involved 27 studies, of which 19 studies reported significant study). Trials were excluded if any participants who were
reduction in state and/or trait anxiety. In women who suffer clinical patients with physical or mental symptoms, shift
9
from anxiety disorders, 2-month yoga class can lead to working personnel, or people with sleep disorder or perinatal
significant reduction in perceived levels of anxiety. 10 women. The reason why we excluded shift-working personnel
The effect of yoga and stress has been examined in wide was that shift workers may suffer extra stress compared with
range of age groups and social status including prisoner and the heathy population with regular life routine. Pregnant
office set. 11,12 The mechanism of yoga and stress has been women who have to go to hospital for regular medical check
underlined. Positive affect, self-compassion, inhibition of the was excluded due to their special body condition. People who
posterior hypothalamus and salivary cortisol from a current undergo sub-health condition (eg, people with sleep
systematic review were all shown to mediate the relationship disorders, insomnia) were also excluded because stress may
between yoga and stress. Due to the diversity of yoga interact with subhealth conditions.
13
practices and the vulnerable evidence existed in yoga types Studies which conducted with multiple or mixed
and stress in healthy populations, the present study sought to research methods were excluded. In addition, we also
better characterize the benefits of yoga on stress. This excluded publication of reviews articles and letter to editors
systematic review evaluates the current scientific evidence of in this study. If multiple published reports from the same
yoga practice on stress. We hypothesize that any types of yoga trial were available, only the report that contain the most
will have beneficial effects on stress. We examined this qualified information were taken into consideration.
question across a large age range. Nevertheless, we did not take the sample size as an exclusion
criterion. Meanwhile, reviews or longitudinal studies were
METHODS not included. The inclusion and exclusion criteria are
To examine our hypothesis, we conducted a systematic presented in Table 1.
review.
Quality Assessment
Databases and Search Terms We used the Critical Appraisal Skills Programme
The PICO standard was used as a supportive guideline (2018) checklist to assess the quality of the selected
16
15
in the study selection. Before assessing by PICO, all studies. These checklists were designed to be used as
manuscripts initially considered relevant by title and abstract educational pedagogic tools, as part of a workshop setting,
were eligible for inclusion. Details in PICO standard: therefore we do not suggest a scoring system. The core

Wang—Yoga and Stress Among Healthy Adults ALTERNATIVE THERAPIES, JUL/AUG 2020 VOL. 26 NO. 4 59