ARE THE CLINICAL EFFECTS OF HOMEOPATHY PLACEBO-EFFECTS - A METAANALYSIS OF PLACEBO-CONTROLLED TRIALS

Background Homoeopathy seems scientifically implausible, but has wides pread use. We aimed to assess whether the clinical effect reported in randomised controlled trials of homoeopathic remedies is equivalent to that reported for placebo. Methods We sought studies from computerise d bibliographies and contacts with researchers, institutions, manufact urers, individual collectors, homoeopathic conference proceedings, and books. We included all languages. Double-blind and/or randomised plac ebo-controlled trials of clinical conditions were considered. Our revi ew of 186 trials identified 119 that met the inclusion criteria. 89 ha d adequate data for meta-analysis, and two sets of trial were used to assess reproducibility. Two reviewers assessed study quality with two scales and extracted data for information on clinical condition, homoe opathy type, dilution, ''remedy'', population, and outcomes. Findings The combined odds ratio for the 89 studies entered into the main meta- analysis was 2.45 (95% CI 2.05, 2.93) in favour of homoeopathy. The od ds ratio for the 26 good-quality studies was 1.66 (1.33, 2.08), and th at corrected for publication bias was 1.78 (1.03, 3.10). Four studies on the effects of a single remedy on seasonal allergies had a pooled o dds ratio for ocular symptoms at 4 weeks of 2.03 (1.51, 2.74). Five st udies on postoperative ileus had a pooled mean effect-size-difference of -0.22 standard deviations (95% CI -0.36, -0.09) for flatus, and -0. 18 SDs (-0.33, -0.03) for stool (both p<0.05). Interpretation The resu lts of our meta-analysis are not compatible with the hypothesis that t he clinical effects of homoeopathy are completely due to placebo. Howe ver, we found insufficient evidence from these studies that homoeopath y is clearly efficacious for any single clinical condition. Further re search on homoeopathy is warranted provided it is rigorous and systema tic.