Open Access

Systematic reviews of complementary therapies – an annotated bibliography. Part 3: Homeopathy

  • Klaus Linde1, 2Email author,
  • Maria Hondras3,
  • Andrew Vickers4,
  • Gerben ter Riet5, 6 and
  • Dieter Melchart1
BMC Complementary and Alternative MedicineBMC series ¿ open, inclusive and trusted20011:4

DOI: 10.1186/1472-6882-1-4

Received: 22 March 2001

Accepted: 20 July 2001

Published: 20 July 2001

Abstract

Background

Complementary therapies are widespread but controversial. We aim to provide a comprehensive collection and a summary of systematic reviews of clinical trials in three major complementary therapies (acupuncture, herbal medicine, homeopathy). This article is dealing with homeopathy. Potentially relevant reviews were searched through the register of the Cochrane Complementary Medicine Field, the Cochrane Library, Medline, and bibliographies of articles and books. To be included articles had to review prospective clinical trials of homeopathy; had to describe review methods explicitly; had to be published; and had to focus on treatment effects. Information on conditions, interventions, methods, results and conclusions was extracted using a pretested form and summarized descriptively.

Results

Eighteen out of 22 potentially relevant reviews preselected in the screening process met the inclusion criteria. Six reviews addressed the question whether homeopathy is effective across conditions and interventions. The majority of available trials seem to report positive results but the evidence is not convincing. For isopathic nosodes for allergic conditions, oscillococcinum for influenza-like syndromes and galphimia for pollinosis the evidence is promising while in other areas reviewed the results are equivocal.

Interpretation

Reviews on homeopathy often address general questions. While the evidence is promising for some topics the findings of the available reviews are unlikely to end the controversy on this therapy.

Introduction

In this third part of our series on systematic reviews in complementary therapies we report our findings on homeopathy. Homeopathy is one of the most widespread forms of complementary medicine worldwide. According to a recent survey 3.4% of Americans have used homeopathy in the past 12 months [1]. It is even more widespread in some European countries [2], some countries in South America, India or Pakistan [3]. This widespread use is in strong contrast with the position held by many in scientific medicine that homeopathy has no effect beyond placebo [4].

The basic principle of homeopathy is the principle of similars: A patient with a specific pattern of symptoms is best treated by a remedy which causes the same or a very similar pattern in healthy subjects. Homoeopathic remedies are often prescribed in high dilutions some of which are unlikely to contain any molecules of the originally diluted agents. In consequence, homoeopathic remedies – at least when applied in high dilutions – cannot act by pharmacological means. Theories for a potential mechanism of action, therefore, postulate the storage of information in the dilution process by physical means [5].

Methods

A detailed description of the methods used in this review of reviews is given in the first part of this series [6]. As a specific intervention-related inclusion criterion we required that reports reviewed prospective (not necessarily controlled) clinical trials of homoeopathic medicines in humans.

Results

From a total of 22 potentially relevant reviews identified in the literature screening, 18 reviews published in 19 papers met the inclusion criteria [725] (see table 1). Four papers were excluded as they were only subgroup or methodological analyses of previously published papers [2629].
Table 1

Systematic reviews of clinical trials of homoeopathy

    

Features

  

Author Year

Indication

Homoeopathy/

Studies

1 / 2 / 3 /

Results

Conclusion

  

Control

 

4 / 5

  

All homoeopathy in all conditions

Cucherat

all

all/placebo

17 RCT

y / y / y /

Combined p value for an effect

There is some evidence that

2000 [7]

   

n /y

over placebo p = 0.000036, for

homoeopathy is more than placebo.

     

best trials only p = 0.08

Studies of high quality more likely to be

      

negative

Linde 97 [8]

all

all/placebo

89 RCT

y / y / y /

OR of all trials over placebo 2.45

Results not compatbile with the

    

y /y

(95%CI 2.05; 2.93), in better trials

hypothesis that all homeo-pathy is

     

1.66 (1.33; 2.08)

placebo. No firm evidence for any

      

single condition

Walach 97

all

all/placebo,

41 RCT

y / p / y /

Random effect size g = 0.259

The effects of homoeopathy are not

[9]

 

conventional

 

y / y

(95%CI -0.319; 0.837), fixed

different from placebo on a statistical

     

effects 0.295 (0.223; 0.366)

level

Lutz 93 [10]

all

all/placebo,

21 RCT/CCT

? / n / y /

Results of available studies

No clear conclusions drawn.

  

conventional

 

y / p

contradictory

(Comment: thesis mainly discussing

      

problems of meta-analysis)

Kleijnen 91

all

all/placebo,

107 CCT

y / p / y /

81 trials reported positive results.

Available evidence positive but not

[11]

 

conventional

 

y / n

Most trials low quality but many

sufficient to draw definitive conclusions

     

exceptions

 

Hill 90 [12]

all

all/placebo,

40 RCT

n / p / y /

The authors of half of the studies

The results do not provide acceptable

  

conventional

 

y / n

concluded that homoeopathy was

evidence that homoeopathy treatments

     

effective, further 7 promising

are effective

Individualized homoeopathy in all conditions

Ernst 99

all

individualized/

3 RCT, 3 CCT

y / p / n /

All trials were burdened with

The relative efficacy of individualized

[13]

 

conventional

 

y / n

serious methodological flaws.

homoeopathy compared to

     

Results non-uniform

conventional treatments is not known

Linde 98

all

individualized/

32 RCT

y / y / y /

Responder RR vs. placebo 1.62

Available evidence suggests effects

[14]

 

placebo, convent.

 

y / y

(95%CI 1.17; 2.23), in better

over placebo. Evidence not convincing

     

quality trials 1.12 (0.87; 1.44)

due to shortcomings and

      

inconsistencies

Various homoeopathic treatments in a single condition/area

Barnes 97

postoperative

various/placebo

4 RCT, 2 CCT

y / y / y /

Time to first flatus in homoeopathy

Available evidence positive but several

[15]

ileus

  

y / y

significantly shorter. Best trial

caveats preclude definitive conclusions

     

negative

 

Ernst 98

delayed-

various/placebo

8 double-blind

y / y / y /

Most trials with severe flaws. The

Published evidence does not support

[16]

onset muscle

 

trials (3

y / n

3 RCT showed no significant

the hypothesis that homoeopathic

 

soreness

 

explicitly RCT)

 

effects over placebo

remedies are effective for muscle

      

soreness

Jacobs 91*

rheumatic

various/placebo

4 CCT

p / y / n /

3 of 4 trials positive. Quality poor

No specific conclusion on

[17]

diseases

  

y / n

 

homoeopathy (generally: no convincing

      

evidence for alternative therapies in

      

rheumat.)

Linde 98

asthma

various/placebo

3 RCT

y / y / y /

Trials highly heterogeneous. Two

Currently available evidence insufficient

[18]

   

y / n

report statistically significant

to assess the possible role of

     

effects

homoeopathy in the treatment of

      

asthma

Arnica in various conditions (mainly various tissue traumata)

Lüdtke 99

all

arnica/placebo,

23 RCT, 14

y / y / y /

Quality often low. 13 of 35 studies

Available evidence suggests that arnica

[19]

 

no treatment

CCT

n / n

vs. placebo with significant results,

can be efficacious. Further rigorous

     

10 with trend

trials needed

Ernst 98

all (mainly

arnica/placebo,

4 RCT, 4 CCT

y / y / y /

2 trials positive, 2 trials positive

Claims that homoeopathic arnica is

[20]

trauma)

conventional

 

y / n

trend. Most studies with severe

efficacious are not supported by

     

flaws

rigorous trials

Similar homoeopathic treatments in one condition/a group of conditions

Taylor

allergic

isopathic

4 RCT

n / n / n /

Pooled analysis of 100 mm visual

Isopathic nosodes were different from

2000** [21]

conditions

nosodes/placebo

 

y / y

analogue scores 9.8 (95%CI

placebo on both subjective and

     

4.2;15.4) mm better with isopathy

objective measures

Vickers

influenza-like

oscillococcinum/

7 RCT

y / y / y /

No evidence for preventative

Oscillococcinum probably reduces the

2000 [22]

syndrome

placebo

 

y / y

effect (3 trials) but reduction of

duration of influenza-like syndromes.

     

length of illness in treatment trials

Further trials needed

Ernst 99

headache

individualized/

4 RCT

y / p / y /

one trial positive, one partially

The trial data do not suggest an effect

[23]

prophylaxis

placebo

 

y / n

positive, 2 negative

over placebo in the prophylaxis of

      

migraine or headache

Wiesenauer

pollinosis

galphimia/placebo

8 RCT, 1 CS,

p / n / n /

Responder RR galphimia vs.

Galphimia is significantly more effective

96** [24,25]

  

2 UCS

y / y

placebo from 7 trials 1.25 (95%CI

than placebo

     

1.09; 1.43)

 

*Disease-focused review on a variety of complementary medicine interventions including homoeopathy; **Meta-analytic overviews of researchers of their own trials on the topic Features: 1 = comprehensive search, 2 = explicit inclusion criteria, 3 = formal quality assessment, 4 = summary of results for each included study, 5 = meta-analysis; y = yes, p = partly, n = no, - = not applicable, ? = unclear RCT = randomized controlled trials, CCT = non-randomized controlled trials, CS = cohort study, UCS = uncontrolled study; OR = odds ratio, RR = rate ratio

Three quantitative meta-analyses addressed the general question whether homeopathy is different from placebo by pooling highly heterogeneous study samples [79]. Study samples and meta-analytic methods differed considerably (total number of trials covered 97). While two reviews reported significant effects of homeopathy [7,8] a third found no effect over placebo in the main analysis [9]. Several years before the publication of these studies a meta-analytic approach had already been tried in a thesis [10]. However, this review is mainly dealing with the problems encountered when trying to pool the data and cannot be interpreted meaningfully with respect to the effectiveness of homeopathy. Two older reviews included both placebo-controlled trials and comparisons with standard treatment [11,12] (total number of trials covered 107). Results were classified in a vote count as positive and negative. The majority of the studies had reported positive results. The conclusions were positive with reservations in one review and ambiguous in the other.

Two reviews focused on individualized homeopathy but were not restricted in terms of conditions investigated. A review of comparisons of individualized homoeopathic and conventional treatment found that only few trials of low quality exist [13]. The other review included mainly placebo-controlled trials [14]. Overall, the results suggested that individualized homeopathy is superior to placebo but when the analysis was limited to studies of better quality the difference was no longer significant.

Four reviews focused on a single condition or a group of conditions but included a variety of homoeopathic treatments [1518]. Positive results have been reported for the treatment of postoperative ilues and asthma but definitive conclusions are not possible.

Arnica is the most often investigated homoeopathic remedy. Typically it is used in conditions involving tissue trauma. Two reviews with slightly different inclusion criteria have been published [19,20] (total number of trials covered 37). While the results of the available trials seem to be contradictory the more comprehensive of the two reviews had slightly more favorable conclusions.

Systematic reviews addressing more focused questions are available for the use of isopathic nosodes (diluted allergens) in allergic conditions, Oscillococcinum for influenza-like syndromes, individualized homeopathy for headache and galphimia for pollinosis [2125]. Significant differences over placebo were reported for all but the headache review.

Discussion

Systematic reviews on homeopathy address, more often than in other areas of complementary medicine, general questions such as "is it more than placebo?" or "is it effective?" This is probably due to the fact that any effect of homeopathy over placebo is considered scientifically implausible. In consequence, the discussion does not primarily focus on specific clinical problems but on whether there is a real effect at all. While many overviews report that the majority of trial results are positive conclusions of reviewers are contradictory.

With few exceptions such as arnica for trauma or individualized homeopathy for headache, the reviews (and probably the primary research) do not cover conditions and treatment approaches which are relevant in homoeopathic practice. Self-medication with Oscillococcinum for influenza-like syndromes is popular in several countries but cannot be considered representative practice.

We want to emphasize again that it was not our primary objective to assess the effectiveness of homeopathy and the other therapies included in our series but to provide an annotated bibliography of the available systematic reviews. This provides an overall picture of the evidence but for an in-depth review readers must go back to the original reviews.

In conclusion, the available systematic reviews on homeopathy provide little guidance for patients and doctors. They rather reflect the ongoing fundamental controversy on this therapy and strengthen the perception that, on one side, positive evidence from clinical trials will not convince skeptics, and that on the other side negative results from trials not representing actual practice will not have any impact on homoeopaths.

Declarations

Acknowledgements

KL's work was partly funded by the NIAMS grant 5 U24-AR-43346-02 and by the Carl and Veronica Carstens Foundation, Essen, Germany. We would like to thank Brian Berman for his support, his help to get funding and his patience in awaiting the completion of our work.

Authors’ Affiliations

(1)
Centre for Complementary Medicine Research, Department of Internal Medicine II, Technische Universität
(2)
Institute for Social Medicine & Epidemiology, Charité Hospital, Humboldt University
(3)
Consortial Center for Chiropractic Research
(4)
Royal London Homoeopathic Hospital
(5)
NHS Centre for Reviews & Dissemination, University of York
(6)
Department of Epidemiology, Maastricht University

References

  1. Eisenberg DM, Davis RB, Ettner SL: Trends in alternative medicine use in the United States, 1990-1997. Results of follow-up national survey. JAMA. 1998, 280: 1569-1575. 10.1001/jama.280.18.1569.View ArticlePubMed
  2. Fisher P, Ward A: Complementary medicine in Europe. BMJ. 1994, 309: 101-111.
  3. Malik IA, Khan NA, Khan W: Use of unconventional methods of therapy by cancer patients in Pakistan. Eur J Epidemiol. 2000, 16: 155-160. 10.1023/A:1007621104789.View ArticlePubMed
  4. Vandenbroucke JP: Homoeopathy trials going nowhere . Lancet. 1997, 350: 824-10.1016/S0140-6736(97)22038-6.View ArticlePubMed
  5. Schulte J: Effects of potentization in aqueous solutions. Br Hom J. 1999, 88: 155-160. 10.1054/homp.1999.0317.View Article
  6. Linde K, Vickers A, Hondras M: Systematic reviews of complementary therapies – an annotated bibliography. Part 1: acupuncture. BMC Complementary and Alternative Medicine. 2001, 1: 3-10.1186/1472-6882-1-3.PubMed
  7. Cucherat M, Haugh MC, Gooch M, Boissel JP: Evidence of clinical efficacy of homeopathy. A meta-analysis of clinical trials. Eur J Clin Pharmacol. 2000, 56: 27-33. 10.1007/s002280050716.View ArticlePubMed
  8. Linde K, Clausius N, Ramirez G, et al: Are the clinical effects of homeopathy placebo effects? A meta-analysis of randomised placebo-controlled trials. Lancet. 1997, 350: 834-843. 10.1016/S0140-6736(97)02293-9.View ArticlePubMed
  9. Walach H: Unspezifische Therapie-Effekte. Das Beispiel Homöopathie. PhD thesis, Psychologisches Institut, Albert-Ludwigs-Universität Freiburg,. 1997
  10. Lutz C: Quantitative Meta-Analyse empirischer Ergebnisse der Homöopathieforschung. Diplomarbeit, Psychologisches Institut, Albert-Ludwigs-Universität Freiburg,. 1993
  11. Kleijnen J, Knipschild P, ter Riet G: Clinical trials of homoeopathy. BMJ. 1991, 302: 316-323.PubMed CentralView ArticlePubMed
  12. Hill C, Doyon F: Review of randomized trials of homoeopathy. Rev Epidém et Santé Publ. 1990, 38: 139-147.
  13. Ernst E: Classical homoeopathy versus conventional treatments: a systematic review. Perfusion. 1999, 12: 13-15. 10.1177/09526959922120225.
  14. Linde K, Melchart D: Randomized controlled trials of individualized homeopathy: a state-of-the art review. J Alt Complement Ther. 1998, 4: 371-388.View Article
  15. Barnes J, Resch KL, Ernst E: Homoeopathy for post-operative ileus: a meta-analysis. J Clin Gastroenerol. 1997, 25: 628-633. 10.1097/00004836-199712000-00016.View Article
  16. Ernst E, Barnes J: Are homoeopathic remedies effective for delayed-onset muscle soreness? A systematic review of placebo-controlled trials. Perfusion. 1998, 11: 4-8.
  17. Jacobs JWG, Rasker JJ, van Riel PLCM, Gribnau FWJ, van de Putte LBA: Alternatieve behandelingswijzen by reumatische aandoeningen; een literatuuronderzoek. Ned Tijdschr Geneeskd. 1991, 135: 317-322.PubMed
  18. Linde K, Jobst K: Homoeopathy for asthma (Cochrane Review). In: The Cochrane Library, Issue 4. 1998, . Oxford: Update Software.
  19. Lüdtke R, Wilkens J: Klinische Wirksamkeitsstudien zu Arnica in homöopathischen Zubereitungen. In: Karl und Veronica Carstens-Stiftung, Jahrbuch Band 5 (1998). Edited by Albrecht H, Frühwald M. Essen: KVC Verlag. 1999, 97-112.
  20. Ernst E, Pittler MH: Efficacy of homoeopathic Arnica. A systematic review of placebo-controlled clinical trials. Arch Surg. 1998, 133: 1187-1190. 10.1001/archsurg.133.11.1187.View ArticlePubMed
  21. Taylor MA, Reilly D, Llewellyn-Jones RH, McSharry C, Aitchison TC: Randomised controlled trials of homoeopathy versus placebo in periennial allergic rhinitis with overview of four trial series. BMJ. 2000, 321: 471-476. 10.1136/bmj.321.7259.471.PubMed CentralView ArticlePubMed
  22. Vickers AJ, Smith C: Homoeopathic Oscillococcinum for preventing influenza and influenza-like syndromes (Cochrane Review). In: The Cochrane Library, Issue 1. 2000, . Oxford: Update Software.
  23. Ernst E: Homeopathic prophylaxis of headaches and migraine? A systematic review. J Pain Symptom Manag. 1999, 18: 353-357. 10.1016/S0885-3924(99)00095-0.View Article
  24. Wiesenauer M, Lüdtke R: A meta-analysis of the homeopathic treatment of pollinosis with Galphimia glauca. Forsch Komplementärmed. 1996, 3: 230-236.View Article
  25. Lüdtke R, Wiesenauer M: Eine Metaanalyse der homöopathischen Behandlung der Pollinosis mit Galphimia glauca. Wien Klin Wochenschr. 1997, 147: 323-327.
  26. Ernst E, Resch KL: Clinical trials of homoeopathy: a re-analysis of a published review. Forsch Komplementärmed. 1996, 3: 85-90.View Article
  27. Ernst E: Are highly dilute homoeopathic remedies placebos?. Perfusion. 1998, 11: 291-292.
  28. Jonas WB, Linde K: Homeopathy and rheumatic disease. Rheum Dis Clin North America. 2000, 26: 117-123.View Article
  29. Linde K, Scholz M, Ramirez G, Clausius N, Melchart D, Jonas WB: Impact of study quality on outcome in placebo-controlled trials of homeopathy. J Clin Epidemiol. 1999, 52: 631-636. 10.1016/S0895-4356(99)00048-7.View ArticlePubMed
  30. Pre-publication history

    1. The pre-publication history for this paper can be accessed here:http://​www.​biomedcentral.​com/​content/​backmatter/​1472-6882-1-4-b1.​pdf

Copyright

© Linde et al; licensee BioMed Central Ltd. 2001

This article is published under license to BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.

Advertisement