Homeopathy is a unique form of so-called 'alternative' (sadly in most cases, for this read: 'not evidence-based') medicine established by a German doctor, Samuel Hahnemann, in the 1790s. It is based on the following principles:
- 'Like cures like' - substances that are similar to a disease- or other biological state-causing agents are most likely to provide a cure. So for example, insomnia might be treated with caffeine.
- The smaller the concentration of the active ingredient, usually in pill or liquid form, the more powerful its potency. Homeopathic convention states that the most powerful treatments are those that have been diluted to such an extent that they contain just one, or even no remaining molecules of the original substance.
- The above theory is based on the idea that water has a 'memory' - so therefore its the dilution process itself, rather than solely the inclusion of a substance, that is argued to have therapeutic effect.
Even without clinical trials, the theory supporting homeopathy is fatally and actually very obviously flawed. Any glass of water, or breath of air, or anything else that I ingest is likely to have once contained all manner of substances, including those that are toxic or thoroughly unpleasant at sufficient doses. Think of where your toilet water goes and where your tap water comes from...so its really implausible to suppose that water can somehow distinguish between the ingredient in question and all the other substances its molecules have ever come into contact with.
If this were true, all our basic scientific understanding of toxicity and principles of medicine, not to mention the laws of physics, would be critically challenged and face urgent re-examination. But the evidence just doesn't support that this is the case. If we accept this kind of reality-bending theory, then there is no distinction between medicine based on evidence and that based on magic, fraud or nonsense.
The weight of scientific evidence falls heavily against the clinical effectiveness of homeopathy. Although some trials might show a positive effect, generally speaking these are of poorer quality than those that show no effect of homeopathic medicines beyond the placebo effect. Homeopaths have a tendency to selectively cite studies that show support, without considering the evidence in its totality. One can only assume that this demonstrates either a very poor calibre of science, or intentional deception.
The problem is that many people, including intelligent, discerning types, cite personal experience of the benefit of homeopathic remedies, and nobody would wish to insult their testimonies, especially those from the desperately ill. However, to deny that their recovery is likely to be due to homeopathic remedies is not to call them stupid or deluded but to give appropriate acknowledgment to the power of placebo and the limits of anecdotal evidence. This has (like everything) been covered extensively by Ben Goldacre, so I won't go into it in any detail here. The placebo effect and the unreliability of personal experience affect us all, often at a level below what we can consciously access, and so it is not something that should be mocked.
Anyway, bearing all this in mind (you'll really need to look into homeopathy further to get a full picture, I haven't covered the purported and often flawed evidential support for it, or its bizarre, ritualistic processes in sufficient detail, but a little Googling should go a long way. Also see the NHS site for a comprehensive overview and introduction to evidence-based medicine), you'd imagine that it would be a fringe practice, generally ignored by and excluded from conventional medicinal authorities...but sadly this isn't the case...
Homeopathy is available on the NHS. There are several NHS homeopathic hospitals and some GP practices offer homeopathic remedies. The Medicines and Healthcare products Regulatory Agency (MHRA), an executive agency of the Department of Health, who according to their own site "enhance and safeguard the health of the public by ensuring that medicines and medical devices work and are acceptably safe [...] Underpinning all our work lie robust and fact-based judgements to ensure that the benefits to patients and the public justify the risks", has allowed homeopathic pills to make medicinal claims.
This decision by the MHRA was recently reviewed by the parliamentary Science and Technology Select Committee, in a pleasantly surprising example of real policy evaluation, attended by an impressive cast including the big BG himself. You can watch it online here. This needs no further comments and should really be watched by anybody interested in the relationship between medicine and policy.
(Highlights are available for those that can't tolerate this level of nerdery and shocking BS spewing by certain contributors here)
