More suitable for a qualitative analysis than a meta-analysis Guang-Hua Lei, Xiangya Hospital, Central South University 11 February 2014 Dear Editors, We have read with interest the recent report by Wang and coworkers  on managing stress and anxiety through qigong exercise in healthy adults. In a systematic review and meta-analysis of earlier randomized controlled trials, the authors conclude to a significant effect of qigong exercise in pooled stress and anxiety for healthy adults based on data from 199 cases and 199 controls. We really appreciate the work which was done by the authors. At a closer look, however, the positive finding loses its luster. Firstly, data were extracted by one main researcher and then verified by another researcher. Any discrepancies were resolved by discussion. However, in this process it caused selector bias of the meta-analysis, because data extraction of the second researcher was not blind and independent . Previous studies showed that the odds of error caused by two authors extracting data independently was reduced significantly, compared with data extraction twice successively . Meanwhile, cochrane handbook suggest professionals of different background extract data, such as an epidemiologist and a clinical expert, to ensure avoiding selection bias . Secondly, the authors indicated that crossover RCTs were excluded because their results are subject to carryover bias. But in the analysis of effects of qigong exercise, the included study of Chow et al.  and Hwang et al.  were both crossover RCTs on anxiety and perceived stress, which also cause carryover bias. Thus, we are not sure whether the two missing RCTs excluded because of crossover should havebeen retrieved in or not. Finally, Seven RCTs met the inclusion criteria. They were conducted in different countries and the characteristics of participants varied in different studies such as age, intervention (frequency), control, duration and relevant outcome measures. As limited number of included studies, especially the differences between research methods, it is not suitable for meta-analysis but qualitative analysis, in order to avoid merging the same kind of research with different results and losing credibility . On the whole, this meta-analysis raises more questions than it answers. To facilitate future assessments of qigong exercise in stress and anxiety, we invite the authors to improve the research that is required to put into perspective the qigong exercise they have recently contributed for stress and anxiety. Above all, we respect the great contributions of the authors and we are pretty sure the results of the data analysis are accurate with no doubt. Reference  Wang, C. W., Chan, C. H., Ho, R. T., Chan, J. S., Ng, S. M., & Chan, C. L. (2014). Managing stress and anxiety through qigong exercise in healthy adults: a systematic review and meta-analysis of randomized controlled trials. BMC Complement Altern Med, 14(1), 8. doi: 10.1186/1472-6882-14-8.  Felson, D. T. (1992). Bias in meta-analytic research. J Clin Epidemiol, 45(8), 885-892.  Meade, M. O., & Richardson, W. S. (1997). Selecting and appraising studies for a systematic review. Ann Intern Med, 127(7), 531-537.  Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org.  Chow, YvonneW.Y., Dorcas, Allen, & Siu, AndrewM.H. (2012). The Effects of Qigong on Reducing Stress and Anxiety and Enhancing Body–Mind Well-being. Mindfulness, 3(1), 51-59. doi: 10.1007/s12671-011-0080-3.  Hwang, E. Y., Chung, S. Y., Cho, J. H., Song, M. Y., Kim, S., & Kim, J. W. (2013). Effects of a briefQigong-based stress reduction program (BQSRP) in a distressed Korean population: a randomized trial. BMC Complement Altern Med, 13, 113. doi: 10.1186/1472-6882-13-113.  O'Sullivan, E. M., & Higginson, I. J. (2010). Clinical effectiveness and safety of acupuncture inthe treatment of irradiation-induced xerostomia in patients with head and neck cancer: a systematic review. Acupunct Med, 28(4), 191-199. doi: 10.1136/aim.2010.002733. Competing interests No competing interests exist.