Diluted evidence: is there anything special with homeopathy?

Last week I participated in the Royal Society MP-Scientist Pairing Scheme where I got a chance to see Westminster from the inside. I was lucky to end up listening to a hearing in the Parliamentary Science and Technology Select Committee about whether the government was really pursuing evidence based medicine when it funds homepathic medicine through NHS and makes MHRA decisions for homeopathy pills. Ben Goldacre was there and has of course written eloquently about the whole thing. While Booths at least admitted they selling the remedies because they made money from them, the proponents tried both to claim clear results in their favor, that statistical measurement methods did not work and that placebo had nothing to do with what they are doing. A particular howler was how one speaker argued that homeopathy should be respected for its 200-year long history, yet it was "still early days" for explaining how or if it worked.

The thing that struck me the most was that the conditions the homeopaths were claiming the treatments were working for – bruising, baby teething – are very minor. Partially this might be a bias since the people present wouldn't want to be on record claiming to treat serious conditions. Yet the evidence seems fairly clear that many homeopathic practictioners do intimate that they have remedies that work for malaria and AIDS. Yet there was little evidence of disciplinary or any other reactions to misbehaving practicioners from the homeopathic organisations. But if there is anything to homeopathy, shouldn't there be some conditions where it produces a effect large enough to be readily noticeable even in a small trial? And conversely, why have no homeopathic remedy ever been dropped due to bad side effects?

The most likely answer is of course that there are no such conditions, no side-effects inherent in the drug, and that people are getting better thanks to the placebo effect and normal healing and then attributing this to the treatment. That there is indeed a sizeable effect but it somehow eludes measurement yet is clear enough to users to notice appears much less likely – especially if we are supposed to swallow that homeopathy users lack the cognitive biases we find in every other human context.

The interesting issue is why homeopathy is given a special status. The UK is not unique in having MHRA approval for homeopathic drugs, similar schemes exist for example in Sweden. To a large degree this is quality assurance ensuring that there is nothing dangerous in the remedy (you don't want to ingest too much silver nitrate, mercury, arsenic or phosphorus). Another reason is historical: homeopathy has been around since before the beginnings of modern medicine, and has managed to "grandfather" into the pharmacopeia. Yet it now has to compete with not just scientific medicine but countless alternatives, from ayurvedic medicine to hypnosis.

The problem with giving homeopathy a special status seems to be that there is nothing beside this historical situation that distinguishes it from the competitors. The evidence base is more or less nonexistent (some complementary medicine types like acupuncture and certain herbs actually does have solid evidence for some claims) and the underlying theory is highly problematic (if dilution amplifies the effect of a dissolved substance, why does lab animals not show paradoxical effects when given different dosages, especially since often drugs are prepared by diluting a concentrated starting solution?)

Hence, it seems unfair to treat homoeopathy differently from any other treatment with the same level of evidence and safety. Traditional Ayurvedic preparations sometimes contain toxic metals, and would presumably benefit from the same quality oversight as homoeopathy. Insofar taxpayer money should be spent on activities with no or little evidence basis (not just a problem in medicine) we should not privilege one over the others.

The problem is that government support often is leveraged into claims of relevance or efficacy. Much was made in the meeting of the fact that France and Germany also support homeopathy. But politicians often know little of science or evidence, and care more about making voters happy. Governments should be careful so they do not inadvertently confuse people: beside their political functions they have epistemic duties.

Apparently the committee meeting was subject to attempted psychic influence from true believers (I would love to hear their views on the ethics of using supernatural side channels to influence government deliberations – is this democratic?). But I guess the presence of a bunch of sceptical researchers on the back row might have interfered.

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