Background:
Sudarshan Kriya yoga (SKY) is one of the proposed breathing techniques, which has proven to be an effective intervention for depression and anxiety in small studies. This study set out to retrieve, appraise and summarize the existing literature to assess the effectiveness of SKY to improve health outcomes in patients with mild to moderate anxiety and depression.

Methods:
A systematic review of the literature was conducted to identify randomized control studies assessing SKY versus pharmacological intervention or placebo in patients with either depression and/or anxiety published from 1998 to June 2020. The studies were identified through database searches. Assessment of the quality of evidence included risk of bias, heterogeneity, directness of the evidence, risk of publication bias and precision of effect estimates.

Results:
The pooled Standardized Mean Difference (SMD) for the effect of SKY on depression was 0.02[-0.20, 0.24] in 6 studies with 388 participants. The pooled SMD for the effect of SKY on anxiety was -0.05 [-0.63, 0.52] based on five studies with 428 participants. The robustness of the results was assisted by a sensitivity analysis that revealed the effect of each study predominantly affected the overall SMD in each clinical outcome. There was also high heterogeneity observed for depression (I2=93%; p < 0.001) and for anxiety (I2=97%; p < 0.001).

Conclusion:
SKY in itself is diverse in nature and when it comes to its overall effectiveness it may be inferred that teaching has shown immense potential in treating depression and anxiety. Many small studies claimed the effects of SKY on a different range of outcomes. It has also shown to be effective among different segments of population with varying physical capabilities. However, future studies are needed to evaluate the short- and long-term impact of SKY on larger samples.