“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 6 such studies on homeopathy:
One was negative – concluding that homeopathy had no effect beyond placebo:5
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
Mathie et al. 2014: ‘Medicines prescribed in individualised homeopathy may have small, specific treatment effects. Findings are consistent with sub-group data available in a previous ‘global’ systematic review. The low or unclear overall quality of the evidence prompts caution in interpreting the findings. New high-quality RCT research is necessary to enable more decisive interpretation.’6
The negative study – known as ‘The Lancet Study’ or ‘Shang paper’ published in 2005 – remains the only global study ever to conclude that homeopathy is no more than a placebo effect.
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 five other papers
b) has attracted widespread criticism for being seriously flawed, and
c) is now out of date and superseded by the 2014 paper by Mathie et al.6
Latest findings by Mathie et al. 2014
The most recent comprehensive systematic review found that, when analysing only the highest quality randomised controlled trials, homeopathic medicines prescribed during individualised treatment are 1.5- to 2.0-times more likely to have a beneficial effect than placebo.6
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.” 7
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.8
The Mathie et al. study includes 151 placebo-controlled randomised trials – 41 more than Shang’s team identified in 2005, but which would have met their inclusion criteria if available at the time.
This demonstrates the extent to which the 10 year-old Shang et al. paper, which now covers only 73% of the eligible trials, has been superseded.
If there are 5 positive studies and only 1 negative study, 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.”
1. Kleijnen J, Knipschild P, ter Riet G. Clinical trials of homeopathy. BMJ, 1991; 302: 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. Mathie RT et al. Randomised placebo-controlled trials of individualised homeopathic treatment: systematic review and meta-analysis. Systematic Reviews, 2014; 3: 142 | Full text
7. 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
8. Lewith G, Professor of Health Research at Southampton University, Letter to the Editor, Positive Health, December 2008 | Full Text