As soon as I write something critical about homeopathy, some people start claiming that I am biased. And as soon as even the most respected institution publishes a report on the subject, homeopaths insist that it is fatally flawed. On such occasions, an almost stereotypical debate tends to ensue which could be stylised by the following dialogue:
Homeopath: the medical establishment is biased against homeopathy.
Sceptic: that’s because the assumptions of homeopathy are not just implausible but fly in the face of science.
Homeopath: never mind plausibility; the crucial question is whether homeopathy works or not.
Sceptic: agreed — and there is no good evidence to show that it does.
Homeopath: this is not true; here is a study that proves homeopathy to be efficacious.
Sceptic: yes, there are several such trials, but one must always consider the totality of the evidence.
Homeopath: you mean one should go by the results of systematic reviews?
Homeopath: guess what, there are several systematic reviews that arrive at positive conclusions.
Sceptic: I know, but either they are not of good quality, or they exclude important evidence.
Homeopath: if you praise the value of systematic review, you cannot deny their findings.
Sceptic: of course I can; have you seen who wrote these articles? They were written by homeopaths or commissioned by the homeopathic lobby – how can we trust such evidence? Look at systematic reviews which do not have these obvious flaws and you will find they all arrive at negative conclusions.
Homeopath: that’s because they were written by anti-homeopaths.
Sceptic: there is no evidence for this claim.
Homeopath: you just don’t want to see it, because you are biased.
Such exchanges can go on forever. In fact, the question whether highly diluted homeopathic remedies are more than placebos has been going on for the last 200 years. Consumers are often bewildered by this endless dispute and many feel that science should have long been able to settle it once and for all.
I believe there might be a way to do just that. What we need is a scientific tool for assessing the available evidence in such a fashion that neither the homeopaths nor the sceptics can possibly refuse to accept the findings. This tool was created some time ago by the Cochrane Collaboration, a worldwide network of volunteers who evaluate the trial evidence on specific subjects.
Several features make Cochrane reviews unique: they follow an extremely rigorous peer-reviewed protocol; the studies they include are assessed in a standardised fashion; the review-authors have to justify why they exclude certain trials; the team of authors always includes experts from the subject in question (which means that reviews of homeopathy are conducted with the help of homeopaths); the extraction of the data is done in a transparent, standardised way; the reviews are carefully peer-reviewed and regularly updated; all reviews are freely accessible for everyone.
Because of these features, there currently is a very broad consensus that, when it comes to judging the efficacy of medical interventions, Cochrane reviews are the best evidence available.
If that is so, it makes sense to ask what exactly Cochrane reviews tell us about homeopathy. Do they agree with the view of the homeopaths or do they confirm what sceptics say?
Currently seven Cochrane reviews are available which specifically focus on homeopathy. The research questions addressed, the number of primary studies included and the main conclusions of these seven articles are listed below:
Does homeopathy work for asthma?
Six trials with a total of 556 people were included. The authors concluded that ‘there is not enough evidence to reliably assess the possible role of homeopathy in asthma.’
Does homeopathy work for dementia?
There were no studies that could be included and the authors concluded that ‘in view of the absence of evidence it is not possible to comment on the use of homeopathy in treating dementia’.
Does homeopathy work for the induction of labour?
Two trials, involving 133 women, were included. The authors concluded that ‘there is insufficient evidence to recommend the use of homoeopathy as a method of induction’.
Does homeopathy work for ADHD?
Four studies with a total of 168 patients were eligible for inclusion. The authors concluded that ‘there is currently little evidence for the efficacy of homeopathy for the treatment of ADHD’.
Does homeopathy alleviate the adverse effects of cancer treatments?
Eight controlled trials with a total of 664 participants met the inclusion criteria. The authors concluded that ‘this review found preliminary data in support of the efficacy of topical calendula for prophylaxis of acute dermatitis during radiotherapy and Traumeel S mouthwash in the treatment of chemotherapy-induced stomatitis. These trials need replicating. There is no convincing evidence for the efficacy of homeopathic medicines for other adverse effects of cancer treatments.’
Does homeopathy work for irritable bowel syndrome?
Three RCTs with a total of 213 participants were included. The authors concluded that ‘a pooled analysis of two small studies suggests a possible benefit for clinical homeopathy, using the remedy asafoetida, over placebo for people with constipation-predominant IBS. These results should be interpreted with caution due to the low quality of reporting in these trials, high or unknown risk of bias, short-term follow-up, and sparse data. One small study found no statistically significant difference between individualised homeopathy and usual care (defined as high doses of dicyclomine hydrochloride, faecal bulking agents and diet sheets advising a high fibre diet). No conclusions can be drawn from this study due to the low number of participants and the high risk of bias in this trial. In addition, it is likely that usual care has changed since this trial was conducted.’
Does homeopathic Oscillococcinum work for influenza?
The authors included six studies: two prophylaxis trials (327 young to middle-aged adults in Russia) and four treatment trials (1,196 teenagers and adults in France and Germany). They concluded that ‘there is insufficient good evidence to enable robust conclusions to be made about Oscillococcinum in the prevention or treatment of influenza and influenza-like illness’.
While the conclusions of these reviews do, of course, differ to some extent, collectively they show quite clearly that they fail to demonstrate that homeopathy works. In the case of the tentatively positive review (number five), the result is due to the inclusion of trials using homeopathic remedies which were not highly diluted. Such remedies can contain sufficient amounts of active molecules to be effective.
So, here we have it: irrefutable evidence showing that highly diluted homeopathic remedies are not supported by the best currently available evidence.
Crucially, this verdict was generated through the cooperation of leading homeopaths and experienced scientists. It should therefore be accepted by everyone; homeopaths who disagree are in denial of the truth. It now seems important to inform the public accordingly. Consumers must be aware of the facts:
— Homeopathy is not evidence-based.
— Claiming otherwise is neither honest nor ethical.
— Further NHS-funding of homeopathy would be a waste of money.
Edzard Ernst, emeritus professor at the University of Exeter, is the author of A Scientist in Wonderland and the awardee of the John Maddox Prize 2015 for standing up for science. He blogs at edzardernst.com.