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Tests of the efficacy of homeopathic remedies

The “balance of evidence” as to whether homeopathy has any effects other than placebo effects depends on who is balancing the evidence. Homeopaths strongly value the evidence of their own experience in treating patients, supported by the satisfaction reported by their patients in surveys; they believe that this is sufficient evidence of efficacy, but also state that most published clinical trials have shown some beneficial effects. A 1991 global meta-analysis of homeopathic clinical trials published in the BMJ (British Medical Journal) of 105 trials, 81 with positive outcomes, concluded that the placebo response could not explain the positive responses, and another meta-analysis published in the Lancet in 1997 drew similar conclusions. Several meta-analyses evaluating the homeopathic treatment of specific diseases have found positive results, including the treatment of childhood diarhea, some post-surgical conditions and respiratory allergies .

Other meta-analyses have suggested that the effect from a homeopathic remedy was no better than a placebo The Cochrane Collaboration is an organisation that publishes meta-analyses of trial results, and most of their analyses of homeopathic treatments indicate some treatment benefits but not adequate statistically significant benefit. The most supportive of their analyses is of the possible benefits of Oscillococcinum for influenza and influenza-like syndromes.

So why is it that most trials report positive outcomes for homeopathy, but some show no effect, and how is it that the positive evidence does not persuade most scientists and leaders of academic medicine? In the U.S.A., The National Center for Complementary and Alternative Medicine (NCCAM) administers public-funded research into alternative medicine , and some studies have reported positive outcomes, but NCCAM's acting deputy director, Jack Killen, said, in a Newsweek article, "There is, to my knowledge, no condition for which homeopathy has been proven to be an effective treatment." . In the U.K., the NHS recognizes that there have been about 200 randomised controlled trials evaluating homeopathy, some show efficacy of treatment and some don't. They conclude, "Despite the available research, it has proven difficult to produce clear clinical evidence that homeopathy works".

Homeopaths believe that such attitudes reflect bias against alternative medicine, and that because homeopathy does not lend itself to controlled trials, those with a negative outcome may be false negatives.

According to critics of homeopathy, the published trials of specific homeopathic remedies have been mostly small and flawed in design While many of these have indicated positive effects, generally, trials that are larger and more rigorous have tended to show little or no statistically significant effects, as was concluded by the authors of the second Lancet study cited above when they re-analyzed these trials

But this does not explain why small trials should have more strongly positive outcomes than large trials. In fact this is a feature of trials of conventional medicine also – and it is believed that the explanation lies mainly in ‘’publication bias’’ – the tendency of trial outcomes to be published only if the outcome is clearly positive; many small trials with negative or inconclusive outcomes simply go unreported, because they are thought to be uninteresting.

In 1999, the government of Switzerland, for a trial period of 5 years, allowed health costs for treatment with homeopathy and four other CAM modalities to be reimbursed under the country’s compulsory health insurance scheme, and set up a programme to evaluate the cost-effectiveness of these treatments (the Complementary Medicine Evaluation Programme (Programm Evaluation Komplementärmedizin, PEK). Under this programme, a team of scientists and practitioners, including a homeopath, conducted an innovative meta-analysis that became the single most cited study of homeopathy, arousing considerable media attention and a storm of protest from homeopaths. The study, which was also published in the Lancet (by Shang et al.) adopted a novel approach; whereas traditional meta-analyses have tried to combine all studies of a given condition, this was a "global" meta-analysis of homeopathy testing the hypothesis that all reported effects of homeopathic remedies are placebo effects. If so, the authors reasoned, then the reports of positive effects reflect publication bias, and if this is the case then the magnitude of such effects should diminish with sample size and study quality, and for the lergest and best studies there should be no effect. They analyzed 110 placebo-controlled homoeopathy trials and 110 matched conventional-medicine trials. Overall, the conventional medicine trials showed some real effect of treatment, in that some effect was still present in the largest and best trials, but the trials of homeopathy remedies did not. The authors concluded that their analysis was consistent with homeopathy being no better than placebo treatment, and controversially suggested that no further research on homeopathy is necessary. The article was accompanied by an unsigned editorial entitled “The end of homeopathy”" and a signed editorial by Jan Vandenbroucke, professor of clinical epidemiology, at Leiden University, theNetherlands This does not mean that that people treated with homeopathy do feel better as a result - the clinical literature clearly shows this, but Vandenbroucke suggested that this could be because its practitioners treatments spend more time with people than doctors do. The Lancet subsequently published a selection of critical correspondence, and received an angry open letter from the Swiss Association of Homoeopathic Physicians (SVHA). which declared:

“The meta-analysis may be statistically correct. But its validity and practical significance can be seen at a glance: not one single qualified homoeopath would ever treat one single patient in clinical practice as presented in any of the 110 analysed trials! The study cannot give the slightest evidence against homoeopathy because it does not measure real individual (classical) homoeopathy. It confounds real homoeopathic practice with distorted study forms violating even basic homeopathic rules.”

In the Shang et al. review, 21 of the homeopathic trials were judged of “high quality”; these, overall, showed a benefit of homeopathic treatment. In the final phase of analysis, the researchers included only the largest of these; the 8 largest homeopathic trials showed that homeopathic treatment was comparable with a placebo, while 6 similarly large conventional medical trials were not compatible with a placebo effect. Of the 8 largest and best homeopathic trials, only one used an individualized approach to treatment, the other seven used a single medicine prescribed to homeopathic treated subjects. Such non-individualized treatment is common in the larger clinical trials (one of the trials even tested a rarely used homeopathic medicine, Thyroidinum, in the treatment of weight-loss, in a previously untested treatment protocol.

Subsequent critics of the Shang et al. analysis have questioned how definitive it actually is, noting that it involved subjective judgements of study quality. The authors of an article in the Journal of Clinical Epidemiology say "This result can be interpreted differently. Following Shang's perspective it can be explained by small study bias (which includes publication bias). In contrast, one may hypothesize that Shang's result is falsely negative." They authors noted that four of the 21 best trials selected by Shang et al. dealt with preventing or treating muscle soreness - these consistently found no benefits to homeopathy, so if it is accepted that homeopathy is not useful in this condition, the remaining 17 trials show an overall significant effect, mainly determined by two trials on influenza-like diseases. Thus they argue that it is still possible that homeopathy might be effective for some conditions and not for others.

Proponents of homeopathy also note that some of the conventional medical studies analysed by Shang et al. may have shown a treatment effect but that some of these have since been withdrawn because of side effects found subsequently. Critics of homeopathy agree - they say that in conventional medicine, treatments are abandoned when trials show them to be ineffective or unsafe, or when a better drug is found; by contrast, no homeopathic treatment has ever been withdrawn after a trial showed it to be ineffective.