Comparison groups in yoga research: a systematic review and critical evaluation of the literature

Abstract

Objectives: Comparison groups are essential for accurate testing and interpretation of yoga intervention trials. However, selecting proper comparison groups is difficult because yoga comprises a very heterogeneous set of practices and its mechanisms of effect have not been conclusively established.

Methods: We conducted a systematic review of the control and comparison groups used in published randomized controlled trials (RCTs) of yoga.

Results: We located 128 RCTs that met our inclusion criteria; of these, 65 included only a passive control and 63 included at least one active comparison group. Primary comparison groups were physical exercise (43%), relaxation/meditation (20%), and education (16%). Studies rarely provided a strong rationale for choice of comparison. Considering year of publication, the use of active controls in yoga research appears to be slowly increasing over time.

Conclusions: Given that yoga has been established as a potentially powerful intervention, future research should use active control groups. Further, care is needed to select comparison conditions that help to isolate the specific mechanisms of yoga's effects.

Keywords: Comparison group; Control group; Randomized controlled trials; Systematic review; Yoga.

Conflict of interest statement

Conflict of Interest Statement: None declared.

Copyright © 2014 Elsevier Ltd. All rights reserved.

Figures

Figure 1

Number of yoga intervention studies using passive and active comparison conditions

Figure 2

Number of Studies with Passive Only Control Conditions versus Studies with Active Comparison Conditions by Year (ending mid-2012)