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“The best studies have shown homeopathy doesn’t work”

By the ‘best studies’ people usually mean comprehensive systematic reviews, which analyse the results from all available randomised controlled trials (RCTs) on a given subject.

There have been six global systematic reviews (SRs) of clinical trials on homeopathy that assessed all types of homeopathic treatment for all available medical conditions together in one paper1-6. Of these SRs, 5 included meta-analysis1-5, whilst 1 (the 2015 NHMRC review)6 did not.

Findings of the 5 SRs with meta-analyses

  • Four SRs were positive – suggesting that there was some evidence of an effect of homeopathy beyond placebo, but more high quality research would be needed to reach definitive conclusions1-4
  • One SR was negative – concluding that homeopathy had no effect beyond placebo5.

Original conclusions from the 5 meta-analysesLess

  • Kleijnen et al. 1991: ‘At the moment the evidence of clinical trials is positive but not sufficient to draw definitive conclusions because most trials are of low methodological quality and because of the unknown role of publication bias. This indicates that there is a legitimate case for further evaluation of homoeopathy, but only by means of well performed trials.’1
  • Linde et al. 1997: ‘The results of our meta-analysis are not compatible with the hypothesis that the clinical effects of homeopathy are completely due to placebo. However, we found insufficient evidence from these studies that homeopathy is clearly efficacious for any single clinical condition. Further research on homeopathy is warranted provided it is rigorous and systematic.’ 2
  • Linde et al. 1999: ‘We conclude that in the study set investigated, there was clear evidence that studies with better methodological quality tended to yield less positive results.’3
  • Cucherat et al. 2000: ‘There is some evidence that homeopathic treatments are more effective than placebo; however, the strength of this evidence is low because of the low methodological quality of the trials. Studies of high methodological quality were more likely to be negative than the lower quality studies. Further high quality studies are needed to confirm these results.’4
  • Shang et al. 2005: ‘Biases are present in placebo-controlled trials of both homoeopathy and conventional medicine. When account was taken for these biases in the analysis, there was weak evidence for a specific effect of homoeopathic remedies, but strong evidence for specific effects of conventional interventions. This finding is compatible with the notion that the clinical effects of homoeopathy are placebo effects.’5

The negative meta-analysis study – known as ‘The Lancet Study’ or ‘Shang paper’ published in 2005 – continues to be cited as evidence that homeopathy is no different to placebo.

So, when people say, “the best studies have shown its no better than placebo”, they rarely realise that they are basing this opinion entirely on one paper which,
a) is contradicted by other papers
b) has attracted widespread criticism for being seriously flawed, and
c) is now out of date.

Additionally, the NHMRC 2015 homeopathy review has attracted international criticism for its flawed methodology  and cannot be considered an accurate or robust summary of the clinical evidence in homeopathy.

Recent developments

Since 2013, overviews and SRs of the clinical evidence in homeopathy have made significant progress in the form of Dr Robert Mathie’s comprehensive review programme, which is nearing completion. This programme of work includes four planned SRs with meta-analysis, each covering all clinical conditions, but with appropriate separation into treatment types and comparators i.e. whether homeopathic treatment is individualised or not, and whether the control group is placebo or ‘other than placebo’.

The first of these comprehensive systematic reviews (published in 2014) found that, homeopathic medicines prescribed during individualised treatment are 1.5- to 2.0-times more likely to have a beneficial effect than placebo.7

MoreLess

The erroneous idea that high quality trials show homeopathy doesn’t work seems to originate from a misunderstanding of the trends seen in two comprehensive systematic reviews (Linde 19972 and Shang 20055which singled out high-quality trials.

Here is what the data in these studies actually tells us:

In 1997 Klaus Linde and co-workers identified 89 clinical trials that showed an overall odds ratio of 2.45 in favor of homeopathy over placebo. There was a trend toward smaller benefit from studies of the highest quality, but the 10 trials with the highest Jadad score still showed homeopathy had a statistically significant effect.” 8

The Shang 2005 study set out to compare the quality of trials in homeopathy and conventional medicine, by looking at 110 similar trials from each of the two disciplines. They assessed 21 of the homeopathy trials and 9 of the conventional trials as being of “higher quality”. Shang’s team decided to analyse only 8 of these high quality trials, which produced the negative result that homeopathy is no better than placebo, but if you analyse all 21 higher quality trials of homeopathy, the results are positive, suggesting that homeopathy does have an effect beyond placebo.9 

If there are positive studies, why do some people still refuse to accept what the evidence says?

The issue appears to be one of ‘plausibility bias’ i.e. those who hold a prior belief that homeopathy is impossible, will view the results of research differently from those who believe homeopathy may work or does work.

As far back as 1991, the authors of the first of these major studies expressed this very clearly in their own paper:1

“The amount of positive evidence even among the best studies came as a surprise to us. Based on this evidence we would be ready to accept that homoeopathy can be efficacious, if only the mechanism of action were more plausible.”

ReferencesLess

1. Kleijnen J, Knipschild P, ter Riet G. Clinical trials of homeopathy. BMJ, 1991302: 960 | PubMed

2. Linde K, et al. Are the clinical effects of homeopathy placebo effects? A meta-analysis of placebo-controlled trials. Lancet, 1997; 350: 834–843 | PubMed

3. Linde K, et al. Impact of study quality on outcome in placebo-controlled trials of homeopathy. Clin Epidemiol, 1999; 52: 631–636 | PubMed

4. Cucherat M, Haugh M C, Gooch M, Boissel J P. Evidence of clinical efficacy of homeopathy. A meta-analysis of clinical trials. HMRAG. Homeopathic Medicines Research Advisory Group. J Clin Pharmacol, 2000; 56: 27–33 | PubMed

5. 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: 726–32 | PubMed

6. Australian National Health and Medical Research Council (NHMRC) 2015 Homeopathy Review | Link

7. Mathie RT et al. Randomised placebo-controlled trials of individualised homeopathic treatment: systematic review and meta-analysis. Systematic Reviews, 2014; 3: 142
 | Full text

8. Hahn RG. Homeopathy: Meta-Analyses of Pooled Clinical Data. Forsch Komplementmed, 2013;20:000–000 Published online: October 17, 2013 DOI: 10.1159/000355916 | PubMed

9. Lewith G, Professor of Health Research at Southampton University, Letter to the Editor, Positive Health, December 2008 | Full Text

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