Table 2.

Effect sizes (SMDs) and confidence intervals for each study included in the meta-analysis. Negative SMDs show a reduction of pain in the treatment group for that study compared with the placebo control group

Study	N (treatment)	N (control)	SMD	95 % CI low	95 % CI high
Bliddal et al. 2000 [42]	56	56	−0.05	−0.42	−0.32
Altman et al. 2001 [43]	124	123	−0.16	−0.41	0.09
Wigler et al. 2003 [44]	29	29	−0.46	−0.98	0.07
Brinkhaus et al. 2005 [56]	24	58	0.23	−0.24	0.71
Black et al. 2010 [37]	20	20	−0.69	−1.33	−0.05
Agarwal et al. 2011 [54]	25	25	−1.73	−2.38	−1.08
Rahnama et al. 2012 [52]	59	46	−1.19	−1.61	−0.77
Panahi et al. 2014 [50]	19	21	−1.65	−2.37	−0.93