Fifteen years of review and meta-analysis

The central tenet of homoeopathy is that homoeopathic treatment has a real effect on health-care outcomes, and this most certainly involves the remedies having an effect beyond placebo.  Individual anecdotes of what virtually amount to miracle cures abound, which would suggest that demonstrating some sort of effect in a controlled trial should be quite simple.  However, that's not quite how it turns out.

There have been quite a few meta-analyses and literature reviews over the years, and the first one was totally negative.

HILL, C. & DOYON, F. (1990)  Review of Randomized Trials of Homoeopathy.  Review D'Epidemilogie et de Sante Publique 38: 139-147.

In our opinion, the results do not provide acceptable evidence that homoeopathic treatments are effective.

The next believed that there might be something there, but couldn't really say because of the poor quality of most of the papers they'd reviewed.  Remember, this is an entire system of medicine, but they couldn't be sure whether there was any effect there at all.

KLEIJNEN, J., KNIPSCHILD, P. & TER RIET, G. (1991)  Clinical Trials of Homoeopathy.  British Medical Journal 302: 316-23.

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.

This paper is at the centre of an interesting phenomenon encountered when debating with homoeopaths.  Frequently, the claim is made that the Kleijnen paper declares "The higher the scientific merit of the study, the more likely it is to show homoeopathy as superior to placebo."  In fact the paper says nothing of the sort.  Proponents are simply repeating without checking the claims on this page from the Faculty of Homoeopathy web site (amusingly occupying the domain "").  One merely wonders if this page represents the Faculty's usual standard of accuracy in reporting.  (Compare the text with the actual abstracts of the papers - linked from here, but, tellingly, not linked to by the Faculty, who clearly prefer to interpret matters to the faithful.)

The next paper to appear is never mentioned by the homoeopaths, and perhaps one can see why.

PRESCRIRE INTERNATIONAL (unattributed articles) (1996)  Homeopathy update.  Prescrire International 5:21.

Despite the large number of comparative trials carried out to date there is no evidence that homeopathy is any more effective than placebo therapy given in identical conditions.

The next paper is the one most cited by homoeopathic proponents.  It's certainly the most positive mainstream publication they've ever had in their favour.  But even this can't say for sure that there's any effect at all!  (And it's getting a bit long in the tooth these days.)

LINDE, K., CLAUSIUS, N., RAMIREZ, G., MELCHART, D., EITEL, F. HEDGES, L. V., & JONAS, W. B. (1997)  Are the Clinical Effects of Homoeopathy Placebo Effects?  A Meta-Analysis of Placebo-Controlled Trials.  Lancet 350: 834-43.

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.

However, several people found the first part of that statement a bit surprising, and had a closer look at the data, with a major Bandolier article presenting a detailed analysis.  The main point at issue was whether indeed there was no decline in the probability of a positive result with increasing quality of study design.  Finally, goaded by the volume of critical comment, the original authors published what virtually amounted to a retraction.

LINDE, K., SCHOLZ M., RAMIREZ, G., CLAUSIUS, N., MELCHART, D., & JONAS, W. B. (1999)  Impact of Study Quality on Outcome in Placebo-Controlled Trials of Homeopathy.  J. Clin. Epidemiol. 52: 7, 631-636.

We conclude that in the study set investigated, there was clear evidence that studies with better methodological quality tended to yield less positive results.

It's striking that when homoeopaths boast about the earlier Linde paper, they never get round to mentioning this one!

The other paper referred to in the Faculty of Homoeopathy page is a 1996 report to the European Commission on homoeopathy.  This is represented as positive, however the 1996 document is not accessible online so it has not been possible to verify the quotes.  They may be no more accurate than the representation of the Kleijnen study.  What is available is the peer-reviewed version which was published in 2000.

CUCHERAT, M., HAUGH, M. C., GOOCH, M. & BOISSEL, J. P. (2000)  Evidence of clinical efficacy of homeopathy.  A meta-analysis of clinical trials.  Eur. J. Clin. Pharmacol. 56(1): 27-33.

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.

A couple of years later another meta-analysis specifically collated the findings of these earlier papers, with particular reference to the plethora of re-analyses of Linde's original data.  Although the author of this review trained as a homoeopath, his opinion is not respected by the homoeopathic community!

ERNST, E. (2002)  A systematic review of systematic reviews of homeopathy.  Br. J. Clin. Pharmacol. 54, 577-582.

Collectively [the reviews] failed to provide strong evidence in favour of homeopathy.  In particular, there was no condition which responds convincingly better to homeopathic treatment than to placebo or other control interventions.  Similarly, there was no homeopathic remedy that was demonstrated to yield clinical effects that are convincingly different from placebo.

The same year, one of a series of reviews published by staff at the NHS Centre for Reviews and Dissemination, University of York, also dealt with the homoeopathy issue.

O'MEARA, S., WILSON, P., BRIDLE, C., KLEIJNEN, J. & WRIGHT, K. (2002)  Homeopathy.  Effective Healthcare 7: 3, 1-12.

There are currently insufficient data either to recommend homeopathy as a treatment for any specific condition, or to warrant significant changes in the provision of homeopathy. .... Any future research evaluating homeopathy should address the methodological inadequacies of the existing evidence base

Or, to put it more simply, the trials the homoeopaths like to boast about are so full of glaring holes that their assertions cannot be supported.  It's interesting to note that Dr. Kleijnen seems to have radically re-evaluated his position in the intervening eleven years.

Another comprehensive literature review was published the following year.

ALMEIDA, R. M. (2003)  A critical review of the possible benefits associated with homeopathic medicine.  Rev. Hosp. Clin. Fac. Med. Sao Paulo, 58, 324-331.

This is very up-to-date, very penetrating, and the homoeopaths don't really seem to want to add it to their favourites list either.

As a result of the recent scientific research on homeopathy, it can be concluded that ample evidence exists to show that the homeopathic therapy is not scientifically justifiable.

The most recent review took a rather different line, comparing published trials of homoeopathy with similar published trials of conventional medications, to see who was winning.

SHANG, A., HUWILER-MUNTENER, K., NARTEY, L., JUNI, P., DORIG, S., STERNE, J. A., PEWSNER, D., & EGGER, M. (2005)  Are the clinical effects of homoeopathy placebo effects?  Comparative study of placebo-controlled trials of homoeopathy and allopathy.  Lancet, 366, 726-732.

There doesn't seem to have been much of a contest.

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.

Does that bit about the "weak evidence for a specific effect" not provide aid and succour to the homoeopaths?  When researchers pay a lot of attention to a person or a group of people, it almost always happens that some effect is observed - the Hawthorne Effect.  This study correctly identifies this feature and comes to the conclusion which is worth repeating.  "This finding is compatible with the notion that the clinical effects of homoeopathy are placebo effects."

This paper triggered a very forthright and blunt editorial in the journal, suggesting that the editor of the Lancet had had enough of the practice of bending over backwards to give every pro-homoeopathy paper full credit for just possibly being on the level.

That homoeopathy fares poorly .... is unsurprising.  Of greater interest is the fact that this debate continues, despite 150 years of unfavourable findings.  The more dilute the evidence for homoeopathy becomes, the greater seems its popularity.  For too long, a politically correct laissez-faire attitude has existed towards homoeopathy, but there are now signs of enlightenment from unlikely sources.  The UK Parliamentary Select Committee on Science and Technology issued a report about complementary and alternative medicine in 2000.  It recommended "any therapy that makes specific claims for being able to treat specific conditions should have evidence of being able to do this above and beyond the placebo effect".  Going one step further, the Swiss Government, after a 5-year trial, has now withdrawn insurance coverage for homoeopathy and four other complementary treatments because they did not meet efficacy and costeffectiveness criteria....

It is the attitudes of patients and providers that engender alternative-therapy seeking behaviours which create a greater threat to conventional care - and patients' welfare - than do spurious arguments of putative benefits from absurd dilutions.  Surely the time has passed for selective analyses, biased reports, or further investment in research to perpetuate the homoeopathy versus allopathy debate.  Now doctors need to be bold and honest with their patients about homoeopathy’s lack of benefit.

Given that this is the attitude now emerging even in human medicine, where the "feel-good" factor generated by the long consultations and the optimistic patter might actually be regarded as beneficial to the patient, how much less justifiable can it be to sanction the practice in veterinary medicine, where even the weak "it's possible there might be something there, but nobody can say for sure" conclusions have never been seriously advanced, and there can surely be no justification for an approach which merely placates the client, leaving the poor animal untreated except for a sugar pill.

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