In order to evaluate the homeopathic treatment system as a whole, meta-analyses can be carried out across different disease patterns.One problem with this approach is that both different clinical pictures and homeopathic remedies are mixed in the statistical evaluation, so that the result does not allow any generalisable conclusions, neither with regard to specific clinical pictures nor to individual homeopathic remedies or treatment strategies. It is evident that this methodological approach would never be applied in conventional treatments (e.g. summarizing and averaging trials in cardiology, oncology, psychiatry etc. all differing in researched treatments and approaches). Nevertheless, such meta-analyses have been performed and remain informative in assessing the homeopathic approach overall.
Meta-analyses across diagnoses and types of homeopathic approaches were performed for randomized controlled trials, i.e. to assess efficacy of homeopathic remedies (whether they exert specific remedy effects beyond placebo). In the following we discuss the most recent and most exhaustive meta-analyses.
Mathie et al. (2014) performed a systematic review and meta-analysis of randomised controlled trials (RCTs) of individualised homeopathic treatment. Thirty-two RCTs were eligible, covering a total of 24 medical conditions. Twenty-two trials had extractable data and were subjected to meta-analysis with a mean odds ratio of 1.53 (p<0.001). Sensitivity analysis yielded stronger treatment effects with decreasing risk of bias. Three trials with reliable evidence yielded an odds ratio of 1.98 (p=0.013). It can be concluded from this analysis that medicines prescribed in individualised homeopathy have specific treatment effects.
Mathie et al. (2017) performed a systematic review and meta-analysis of randomised controlled trials (RCTs) of non-individualised homeopathic treatment. Fifty-four trials had extractable data: pooled SMD was –0.33 (p<0.001), which was reduced to –0.16 (p<0.023) after adjustment for publication bias. Though three trials with reliable evidence yielded a non-significant pooled SMD: –0.18 (95% CI –0.46, 0.09), a risk of bias analysis yielded no significant difference between studies rated as ‘low’, ‘uncertain’ or ‘high’ risk of bias (p = 0.417). Sub-group analyses yielded no significant differences. Due to the conflicting results of the different evaluation approaches, the high number of included indications, and the low number of replication trials for each indication, the overall meta-analysis does not arrive at consistent and meaningful conclusions.
Mathie et al. (2018) performed a systematic review and meta-analysis of randomised controlled trials of individualised homeopathic treatment with comparison groups other than placebo (e.g. another or no treatment). Eleven RCTs representing 11 different medical conditions were included in the study. Most trials were rated as having ‘high risk of bias’ overall. It is to be concluded that due to the small number and the heterogeneity of studies, no meaningful overall interpretation of the studies was possible.
Mathie et al. (2019) performed a systematic review and meta-analysis of randomised controlled trials of non-individualised homeopathic treatment in which the comparison group received other treatment than placebo (e.g. other or no treatment). Ten trials provided extractable data for meta-analysis. However, the authors concluded that “significant heterogeneity undermined the planned meta-analyses or their meaningful interpretation”.
Summarizing, three attempts to analyse the specific efficacy of homeopathic preparations in overall meta-analyses of randomized controlled trials across all possible indications did not arrive at meaningful conclusions due to the large heterogeneity of the available trials. Thus, it was neither possible to reject nor to retain the hypothesis that homeopathic preparations are equal to placebo. However, one meta-analysis of randomised controlled trials (RCTs) of individualised homeopathic treatments found that such treatments, provided by a trained homeopath, yielded an overall significant effect in favour of homeopathy.