Homeopathy: what does the “best” evidence tell us?

Edzard Ernst
Med J Aust 2010; 192 (8): 458-460. || doi: 10.5694/j.1326-5377.2010.tb03585.x
Published online: 19 April 2010

The debate about the value of homeopathy — a therapeutic method that often uses highly diluted preparations of substances whose effects when administered to healthy subjects correspond to the manifestation of the disorder in the unwell patient1 — is as old as homeopathy itself. In recent decades, about 150 controlled clinical trials of homeopathy have been published. The results were neither all negative nor all positive. In such situations, some commentators resort to “cherry picking” — choosing those findings that fit their own preconceptions. The problem of selective citation is most effectively overcome by evaluating all reliable evidence, an aim best met by systematic reviews.

Even at the level of systematic reviews, the evidence on homeopathy is not entirely uniform. For instance, a Lancet review of 1997 concluded that “the clinical effects of homeopathy are not completely due to placebo”,2 while another systematic review, published in the same journal in 2005, concluded that “the clinical effects of homeopathy are placebo effects”.3 In 2002, I conducted a systematic review of 17 systematic reviews and concluded that “the best clinical evidence for homeopathy available to date does not warrant positive recommendations of its use in clinical practice”.4

Homeopaths have argued that systematic reviews that fail to generate positive conclusions about homeopathy are biased.5 It is therefore necessary to seek out those systematic reviews of research into homeopathy that are least likely to be biased. Several authors have demonstrated that Cochrane reviews tend to be superior to other reviews; they are more rigorous, more transparent, less biased and more up to date.6 In a word, they might be considered the “best”. Therefore, the aim of this article is to summarise and appraise the findings from Cochrane reviews of studies of homeopathy.


The search generated 13 hits. I excluded four articles because they were not specifically about homeopathy,7-10 and three because they were protocols of systematic reviews in progress. Six systematic reviews were included (Box).11-16

The six articles that met the inclusion criteria related to the following conditions: cancer,11 attention-deficit hyperactivity disorder,12 asthma,13 dementia,14 influenza15 and induction of labour.16 Most were authored or coauthored by homeopaths. Key data from these reviews are summarised in the Box. None of these articles concluded that homeopathy is an effective treatment. One review15 was recently withdrawn from the database as the authors were unable to update it. For the purpose of this overview, I have therefore used the 2006 version of that article.15


Collectively, the six reviews that I appraised failed to provide compelling evidence for the effectiveness of homeopathic remedies. These reviews, being Cochrane reviews, are likely to be more reliable than other sources of evidence.6 Furthermore, as most were authored by homeopaths, it seems unlikely that they were biased against homeopathy. In fact, one might argue that they were biased in favour of homeopathy. For instance, the conclusion that “it is not possible to comment . . .”14 on the basis of an “empty” review (a review that did not include a single primary study) might have been phrased more critically. The authors could have pointed out that, whenever no trial data exist, it makes little sense to use homeopathy (or any other therapy) for dementia (or any other condition).

Many systematic reviews of homeopathy have been published outside the Cochrane database. Most arrive at similarly negative conclusions3,4,17 and, in recent years, the evidence seems to have become less and less convincing.18 Numerous authors have pointed out that the main assumptions of homeopathy are biologically implausible.19 Reviewers of basic research studies of homeopathy have noted the low quality of the data and lack of replications,20 and others have concluded that “no positive result was stable enough to be reproduced by all investigators”.21 These findings indicate that homeopathic remedies are unlikely to have clinical effects beyond placebo. Homeopaths tend to deny this and produce lower-level evidence to the contrary.22,23 Closer inspection of this evidence, however, regularly reveals bias. For instance, one reviewer deliberately set out to select only the positive evidence and omit all negative evidence.22

Homeopaths also point to observational studies that seem to suggest that homeopathy is effective.23 Some then tend to interpret the discrepancy between this evidence and that from controlled studies in a most unusual way: they claim it shows that the controlled clinical trial is not suited for the study of homeopathy and that observational data demonstrate the true value of homeopathy.23 A more rational explanation would be that the positive outcomes of observational studies are caused by the non-specific effects of homeopathic treatments (eg, the empathic and lengthy consultation typical of homeopathic services), while the controlled trials demonstrate that homeopathic remedies are placebos.21,24,25

The Cochrane review by Kassab and colleagues11 found preliminary evidence in support of homeopathy (Box). This evidence resulted from studies of material dilutions. However, if dilutions are prepared according to homeopathic rules, they are technically homeopathic remedies even if they are not highly diluted. This means that, while a typical homeopathic remedy is devoid of pharmacologically active ingredients, some homeopathic remedies do contain active molecules. One could thus manufacture a homeopathic preparation of aspirin that is pharmacologically identical to conventional aspirin. It is not surprising that such medicines can have pharmacological effects, but concluding that homeopathic medicines are effective, on the basis of such data, would be misleading.

In conclusion, the most reliable evidence — that produced by Cochrane reviews — fails to demonstrate that homeopathic medicines have effects beyond placebo.

Cochrane systematic reviews of studies of homeopathy

First author (year published)


Stated objective

No. of included
trials (total no. of patients)

Authors’ conclusions



Adverse effects of cancer treatments

“Evaluate effectiveness and safety of homeopathic medicines used to prevent or treat adverse effects of cancer.”

8 (664)

“This review found preliminary data in support . . .”

The two remedies supported by good evidence were not highly diluted


Attention-deficit hyperactivity disorder

“To assess the safety and effectiveness of homeopathy as a treatment for attention-deficit hyperactivity disorder.”

4 (168)

“There is currently little evidence for the efficacy of homeopathy . . .”

No significant benefit


Chronic asthma

“ . . . to assess the effects of homeopathy in people with chronic stable asthma.”

6 (556)

“There is not enough evidence ...”

No significant benefit



“To evaluate the effectiveness and safety profile of homeopathically prepared medications used in treating dementia . . .”

0 (0)

“. . . it is not possible to comment on the use of homeopathy in treating dementia.”

An “empty” review (no primary data)


Oscillococcinum for preventing and treating influenza and influenza-like syndromes

“Determine whether homoeopathic Oscillococcinum or similar medicines are more effective than placebo in the prevention and treatment of influenza and influenza-like syndromes”

7 (2265)

“Though promising the data were not strong enough . . .”

Only review to include a meta-analysis; no significant benefit


Induction of labour

“To determine the effects of homoeopathy for third trimester cervical ripening or induction of labour.”

2 (133)

“There is insufficient evidence to recommend the use of homeopathy as a method of induction”

Both primary studies were flawed; no significant benefit

Received 30 September 2009, accepted 19 January 2010

  • Edzard Ernst1

  • Complementary Medicine, Peninsula Medical School, University of Exeter, Exeter, United Kingdom.


Competing interests:

None identified.

  • 1. Ernst E, Pittler MH, Wider B, Boddy K. The desktop guide to complementary and alternative medicine. 2nd ed. Edinburgh: Elsevier Mosby, 2006.
  • 2. Linde K, Clausius N, Ramirez G, et al. Are the clinical effects of homoeopathy placebo effects? A meta-analysis of placebo-controlled trials. Lancet 1997; 350: 834-843.
  • 3. Shang A, Huwiler-Muntener K, Nartey L, et al. Are the clinical effects of homoeopathy placebo effects? Comparative study of placebo-controlled trials of homoeopathy and allopathy. Lancet 2005; 366: 726-732.
  • 4. Ernst E. A systematic review of systematic reviews of homeopathy. Br J Clin Pharmacol 2002; 54: 577-582.
  • 5. Rutten AL, Stolper CF. The 2005 meta-analysis of homeopathy: the importance of post-publication data. Homeopathy 2008; 97: 169-177.
  • 6. Olsen O, Middleton P, Ezzo J, et al. Quality of Cochrane reviews: assessment of sample from 1998. BMJ 2001; 323: 829-832.
  • 7. Smith CA, Collins CT, Cyna AM, Crowther CA. Complementary and alternative therapies for pain management in labour. Cochrane Database Syst Rev 2006; (4): CD003521. doi: 10.1002/14651858.pub2.
  • 8. Glazener CM, Evans JH, Cheuk DK. Complementary and miscellaneous interventions for nocturnal enuresis in children. Cochrane Database Syst Rev 2005; (2): CD005230. doi: 10.1002/14651858.
  • 9. Gagnier JJ, van Tulder M, Berman B, Bombardier C. Herbal medicine for low back pain. Cochrane Database Syst Rev 2006; (2): CD004504. doi: 10.1002/14651858.pub3.
  • 10. van der Wouden JC, Menke J, Gajadin S, et al. Interventions for cutaneous molluscum contagiosum. Cochrane Database Syst Rev 2006; (2): CD004767. doi: 10.1002/14651858.pub2.
  • 11. Kassab S, Cummings M, Berkovitz S, et al. Homeopathic medicines for adverse effects of cancer treatments. Cochrane Database Syst Rev 2009; (2): CD004845. doi: 10.1002/14651858.pub2.
  • 12. Heirs M, Dean ME. Homeopathy for attention deficit/hyperactivity disorder or hyperkinetic disorder. Cochrane Database Syst Rev 2007; (4): CD005648. doi: 10.1002/14651858.pub2.
  • 13. McCarney RW, Linde K, Lasserson TJ. Homeopathy for chronic asthma. Cochrane Database Syst Rev 2004; (1): CD000353. doi: 10.1002/14651858.pub2.
  • 14. McCarney R, Warner J, Fisher P, Van Haselen R. Homeopathy for dementia. Cochrane Database Syst Rev 2003; (1): CD003803. doi: 10.1002/14651858.
  • 15. Vickers AJ, Smith C. Homoeopathic Oscillococcinum for preventing and treating influenza and influenza-like syndromes. Cochrane Database Syst Rev 2006; (3): CD001957. doi: 10.1002/14651858.
  • 16. Smith CA. Homoeopathy for induction of labour. Cochrane Database Syst Rev 2003; (4): CD003399. doi: 10.1002/14651858.
  • 17. Altunc U, Pittler MH, Ernst E. Homeopathy for childhood and adolescence ailments: systematic review of randomized clinical trials. Mayo Clin Proc 2007; 82 (1): 69-75.
  • 18. Ernst E, Pittler MH, Wider B, Boddy K. Homeopathy: is the evidence-base changing? Perfusion 2006; 19: 380-382.
  • 19. Ernst E, editor. Healing, hype or harm? A critical analysis of complementary or alternative medicine. Exeter: Imprint Academic, 2008.
  • 20. Linde K, Jonas WB, Melchart D, et al. Critical review and meta-analysis of serial agitated dilutions in experimental toxicology. Hum Exp Toxicol 1994; 13: 481-492.
  • 21. Witt CM, Bluth M, Albrecht H, et al. The in vitro evidence for an effect of high homeopathic potencies — a systematic review of the literature. Complement Ther Med 2007; 15 (2): 128-138.
  • 22. European Network of Homeopathy Researchers. An overview of positive homeopathy research and surveys. March, 2007.
  • 23. Spence DS, Thompson EA, Barron SJ. Homeopathic treatment for chronic disease: a 6-year, university-hospital outpatient observational study. J Altern Complement Med 2005; 11: 793-798.
  • 24. Ernst E. The truth about homeopathy. Br J Clin Pharmacol 2008; 65: 163-164.
  • 25. Overall KL, Dunham AE. Homeopathy and the curse of the scientific method. Vet J 2009; 180: 141-148.


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