Are Indian yoga trials more likely to be positive than those from other countries? A systematic review of randomized controlled trials.

OBJECTIVE

To determine whether the conclusions of randomized controlled trials (RCTs) of yoga are more likely to be positive when they were conducted in India and/or when they are published in complementary and alternative medicine (CAM) specialty journals.

METHODS

Medline/PubMed, Scopus, the Cochrane Library, IndMED, and the tables of content of yoga specialty journals not listed in medical databases were screened through February 2014 for RCTs comparing yoga interventions to non-yoga interventions. The RCTs' conclusions were classified as positive (yoga is helpful for a respective condition) or not positive; and compared between RCTs that were a) conducted in India vs. outside India, and b) published in a CAM specialty journal or another type of journal.

RESULTS

A total of 306 RCTs were included; 131 from India and 175 from other countries; and 84 from CAM specialty journals and 222 from other types of journals. Positive conclusions were reached in 277 RCTs (91%); with more positive RCTs being conducted in India than elsewhere (odds ratio=24.8; 95% confidence interval=3.3, 184.5; p<0.001) while type of journal was not associated with the direction of the conclusions (odds ratio=1.2; 95% confidence interval=0.5, 2.9; p=0.828).

CONCLUSIONS

RCTs on yoga that are conducted in India have about 25 times the odds of reaching positive conclusions as those conducted elsewhere. Indian trials should be dealt with carefully when evaluating the helpfulness of yoga for patients in other countries and vice versa.