Current issues of ACP Journal Club are published in Annals of Internal Medicine


Review: Weak evidence shows that homeopathy can be effective

ACP J Club. 1991 May-June;114:83. doi:10.7326/ACPJC-1991-114-3-083

Source Citation

Kleijnen J, Knipschild P, ter Riet G. Clinical trials of homeopathy. BMJ. 1991;302:316-23.



To review the evidence from clinical trials about the efficacy of homeopathy.

Data sources

Citations were retrieved from MEDLINE, 1966 to 1990 (keyword, homeopathy); references in articles and books, journals, libraries and conference proceedings on homeopathy; and personal communications with researchers and homeopathy-product manufacturers.

Study selection

Trials were eligible if parallel index and control groups were included or if there was a crossover design: 107 studies (68 of which were randomized) met these criteria. Animal studies were excluded.

Data extraction

The methodology of studies was rated by ≥ 2 reviewers for description of patient characteristics, number of patients analyzed, randomization, description of the intervention, double-blinding, effect measurement, and presentation and analysis of results.

Main results

On a 100-point scale, 16 studies scored ≥ 60 points; 11 of these 16 showed positive effects of treatment. Of all 105 trials with interpretable results, 81 indicated positive results and a positive trend regardless of the quality of the trial or the variety of homeopathy used, mostly in comparison with placebo. In 24 trials, no positive effects of homeopathy were found. Success of double-blinding was not checked in any trial. Regimens were largely unstandardized across studies and manufacturers of homeopathic products. Only 14 trials tested a classical form of homeopathy and only 1 of these was well designed. This study showed a benefit of homeopathic therapy, in comparison with placebo, for persons with migraine. Several groups of indications were shown for conventional diagnoses, including those of the respiratory system (infections, [19 trials] hay fever, [5 trials] and asthma [1 trial]), gastrointestinal symptoms [7 trials], and pain from several sources [27 trials]. After the earlier publication of several trials that showed a decrease of time to recovery of bowel movements after bowel surgery, a more rigorous trial found no differences. Among other well-designed trials, positive results were found for the duration of obstetric delivery, for improvement of nasal symptoms from pollinosis and pain from ankle sprains, but not for sinusitis or prevention of influenza or postoperative infections; different trials showed conflicting results for the treatment of influenza.


Evidence from clinical trials of homeopathy is generally positive but many of the trials are of low methodologic quality.

Source of funding: Dutch Ministry of Welfare, Public Health, and Cultural Affairs.

Address for article reprint: Dr. J. Kleijnen, Department of Epidemiology and Health Care Research, University of Limburg, P.O. Box 616, 6200 MD Maastricht, the Netherlands.


North American physicians cope with a variety of fads in medicine but are not generally familiar with homeopathy, which, to some, may conjure up visions of herbs, leeches, and other archaic treatments. Homeopathy is based on "like curing like." Depending on the symptom, a substance that causes the same symptom is chosen. The extracted substance is mixed repeatedly with alcohol until an almost infinitely diluted solution is obtained. In some cases, the dose may not contain even a single molecule of active substance, but homeopathists believe that the more dilute the solution, the more potent it is.

Although homeopathy was popular in North America 100 years ago, it gradually fell into disfavor because of the lack of logical explanatory principles. However, homeopathy is used, particularly in Europe, by many physicians despite arguments from skeptical colleagues, and homeopathic products are widely available to consumers.

Kleijnen and colleagues did a commendable job of finding and appraising the literature on homeopathy, using comprehensive criteria for quality. Most, but not all, of these studies were of mediocre to poor quality, but this is also true of studies of allopathic medicine. Poor study methodology and publication bias (studies with negative results being less likely to be published) may have contributed to the large number of positive results among these studies.

How does this affect the practicing physician? In North America homeopathy has little effect, and unless more high-quality, positive evidence becomes available, this should not change. Evidence from large studies is important to show the efficacy of these treatments, but single patient trials (1) may also be helpful for individual patients who believe in homeopathy.

Michael Frasca, MD
College of Medicine at PeoriaPeoria, Illinois, USA


1. Guyatt G, Sackett D, Taylor DW, et al. Determining optimal therapy—randomized trials in individual patients. N Engl J Med. 1986;314:889-92.