Objective: The study aims to investigate the effectiveness of yoga on negative emotions in breast cancer patients. Methods: Pubmed, Elsevier, Web of Science, Cochrane Library, CBM, CNKI, Wanfang, and VIP databases were screened throughout October 2015. Randomized control trials (RCTs) examining the effects of yoga versus a non-exercise or waitlist control group on negative moods in breast cancer patients were included. The methodological quality of included RCTs was evaluated by using the

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... ne Handbook 5.1, and data were analyzed using the Review Manager 5.3. Results: A total of 21 RCTs with 1762 participants were included. We found evidence for immediate effects on anxiety (p < 0.00001), depression (p < 0.00001), distress (p < 0.00001), perceived stress (p < 0.00001), and emotional well-being (p ¼ 0.0002). Sustained effects (3 months) were only found in depression (p ¼ 0.004) but not anxiety (p ¼ 0.43), and other outcomes were not synthesized because of heterogeneity and the limited number of studies. Conclusion: Yoga is valuable in improving negative moods in patients with breast cancer. We also concluded five key mechanisms of yoga therapy in improving negative moods. Further well-designed RCTs with large sample size and long-term follow-up are needed.