3. Effect of placebo interventions across all clinical conditions (continuous outcomes).
| All trials | Trials with low risk of bias | Quality of the evidence | |||||
| Outcomes |
Standardised mean difference (95% CI) |
No. of participants (studies) | Comments |
Standardised mean difference (95% CI) |
No. of participants (studies) | Comments | |
| All clinical conditions | ‐0.23 (‐0.28 to ‐0.17) | 10,525 (158) | Asymmetrical funnel plot Moderate heterogeneity |
‐0.38 (‐0.55 to ‐0.22) | 1610 (11) | Substantial heterogeneity. Four German acupuncture trials had a pooled SMD ‐0.68 (‐0.85 to ‐0.50), whereas 7 other trials had a pooled SMD of ‐0.19 (‐0.31 to ‐0.07) | Moderate |
| Trials with patient‐reported outcomes | ‐0.26 (‐0.32 to ‐0.19) | 8000 (109) | Asymmetrical funnel plot Moderate heterogeneity |
‐0.39 (‐0.57 to ‐0.22) | 1543 (10) | Substantial heterogeneity (see above). | Moderate |
| Trials with observer‐reported outcomes | ‐0.13 (‐0.24 to ‐0.02) | 2513 (49) | Asymmetrical funnel plot Moderate heterogeneity |
‐0.25 (‐0.73 to 0.23) | 67 (1) | One small trial | Moderate |