“Are the clinical effect of homeopathy placebo effects?”;
Are the clinical effect of homeopathy placebo effects?
Homeopathy is a widely used alternative therapy, but its efficacy is still controversial. Homeopathy is based on two main principals. According to the first law, the law of similars, patients with particular symptoms can be treated with substances that in healthy people would produce the same effects as the disease produces. For example, streaming eyes due to hay fever can be relieved with onions. The second principle, the law of infinitesimal doses, states that the biological activity of homeopathic remedies can be improved by extreme dilution. In general, homeopathic substances are repeatedly diluted with water or alcohol, commonly to the extent that no molecules remain. Proponents of homeopathy believe that information is thought to be transferred from the substance to water or alcohol and thus a ‘memory’ of the substance is retained when there are no molecules present. At the moment, no scientific explanation for the mechanism of action of homeopathy is universally accepted. Many people assume that any effects that homeopathy produces, must be non-specific placebo effects. In this critical study, a study on the effects of homeopathy by Shang et al will firstly be summarized/discussed and will be followed by a critical analysis.
The study on homeopathy by Shang et al, published in The Lancet on 27/8/2005, investigated the clinical effects of homeopathy and conventional medicine by performing a meta-analysis. In order to examine the effects of homeopathy and conventional medicine, 110 placebo-controlled homeopathy trials and 110 placebo-controlled conventional medicine trials were included. The homeopathy trials and conventional medicine trials were matched for the enrollment of patients with similar disorders and the assessment of similar outcomes. For each homeopathy trial, matching trials of conventional medicine that enrolled patients with similar disorders and assessed similar outcomes were identified. To assess the clinical effectiveness from homeopathy and conventional medicine trials, the results of both homeopathic and conventional medicine studies were separately combined and analyzed using a meta-analysis. In addition, variables such as publication type and study quality, were also considered using a meta-regression analysis. Subsequently, the results were expressed on odds ratios. Odds ratios below 1.0 indicated a beneficial effect of treatment in all cases. Furthermore, the study argued that publication bias and low methodological quality of the trials could be possible explanations for positive findings of placebo-controlled trials for both interventions. The study states that these biases are more likely to affect small than large studies. In order to reduce the influences of the presence of biases on the effects of the interventions, the study analyzed the results of larger trials of higher quality, which were trials least affected by these biases. The studies were selected for quality criteria such as randomization, masking and data-analysis, and for study size. This resulted in the inclusion of eight homeopathy trials and six conventional medicine trials.
The results showed that the odds ratios of both homeopathy and conventional medicine was below 1.0 for almost all study characteristics. These results indicated beneficial effects of both interventions in comparison with the placebo group. When the analysis was restricted to the larger trials of higher quality, the odds ratios of the meta-analysis was 0.88 based on eight homeopathy trials and 0.58 based on six conventional medicine trials. In contrast to the analysis in which all studies were included, the results of analysis based on larger trials of higher quality indicated that homeopathy did not show beneficial effects in comparison with placebo. However, the effects of conventional medicine remained beneficial.
In summary, the study compared the effects of homeopathy and conventional medicine and estimated results in trials least affected by biases. The study hypothesized that the positive effects of homeopathy could be explained by both methodological deficiencies and biased reporting. The study concludes that their results confirm these hypotheses: the effects of homeopathy were not superior to placebo, whereas the beneficial effects of conventional medicine remained when the analysis was restricted to large trials of higher quality. The main conclusion of the study was thereby that the clinical effects of homeopathy were unspecific placebo effects.
Finally, I wish to raise some concerns about the meta-analysis of homeopathy by Shang et al. Firstly, the main conclusion ‘the clinical effect of homeopathy are placebo effects’ is based on only eight homeopathy trials and six conventional medicine studies. The outcome of the analysis restricted to larger trials of higher quality could easily be due to change. In addition, the study ignores their results in which all clinical studies were included and that indicate that homeopathy does have beneficial effects. A second point of critique is that the article is not transparent and information is missing. Firstly, the article claims that the 110 homeopathy trials and 110 conventional medicine trials are matched, but the matching criteria are not clearly stated in the article. At least one crucial parameter, the trial quality, was not matched. In addition, the article does not mention anything about matching between the eight homeopathy trials and six conventional medicine trials and this indicates that these trials will probably be unmatched. Secondly, the eight large homeopathy trials of higher quality are not referenced and no details about them is given. A study should be reproducible and this is not the case for this study. The classical interventions have been largely proven to be efficacious, because the drugs have been widely examined in pharmalogical stages of drugs testing. In contrast, very few placebo-controlled trials in homeopathy have been performed, which is why there is an absence of evidence that homeopathy is efficacious.