A systematic scoping review of yoga intervention components and study quality

The scientific study of yoga requires rigorous methodology. This review aimed to systematically assess all studies of yoga interventions to (1) determine yoga intervention characteristics; (2) examine methodologic quality of the subset of RCTs; and (3) explore how well these interventions are reported.

Searches were conducted through April 2012 in PubMed, PsycINFO, Ageline, and Ovid's Alternative and Complementary Medicine database using the text term yoga, and through handsearching five journals. Original studies were included if the intervention (1) consisted of at least one yoga session with some type of health assessment; (2) targeted adults aged ≥18 years; (3) was published in an English-language peer-reviewed journal; and (4) was available for review.

Of 3,062 studies identified, 465 studies in 30 countries were included. Analyses were conducted through 2013. Most interventions took place in India (n=228) or the U.S. (n=124), with intensity ranging from a single yoga session up to two sessions per day. Intervention lengths ranged from one session to 2 years. Asanas (poses) were mentioned as yoga components in 369 (79%) interventions, but were either minimally or not at all described in 200 (54%) of these. Most interventions (74%, n=336) did not include home practice. Of the included studies, 151 were RCTs. RCT quality was rated as poor.

This review highlights the inadequate reporting and methodologic limitations of current yoga intervention research, which limits study interpretation and comparability. Recommendations for future methodology and reporting are discussed.