Ben Goldacre, Saturday 28 November 2009, The Guardian

This week the parliamentary science and technology select committee looked into the evidence behind the MHRA’s decision to allow homeopathy sugar pill labels to make medical claims without evidence of efficacy, and the funding of homeopathy on the NHS. There were some comedy highlights, as you might expect from any serious enquiry into an industry where sugar pills have healing powers conferred upon them by being shaken with one drop of the ingredient which has been diluted, so extremely, that it equates to one molecule of the substance in a sphere of water whose diameter is roughly the distance from the earth to the sun.

The man from Boots said he had no evidence that homeopathy pills worked, but he sold them because people wanted to buy them. The man from the pill manufacturers association said negative trials about homeopathy were often small, with an average of 65 people in them, and “all statisticians” agree that you need 500 people for a proper trial. Not only is this untrue (it depends on the effect size, if you claimed your pill cured an incurable condition in every single case, then a dozen patients would be too many): he then joyfully careered on to cite, in his favour, a positive homeopathy trial with just 25 patients in it.

But the best moment was Dr Peter Fisher from the Royal London Homeopathic Hospital (funded by the NHS) explaining that homeopathic sugar pills do actually have physical side effects: so they must be powerful.

Can a sugar pill have a side effect? Interestingly, a paper published in the journal Pain next month looks at just this issue. They found every single placebo-controlled trial ever conducted on a migraine drug, and looked at the side effects reported by the people in the control group, who received a dummy “placebo” sugar pill instead of the real drug. Not only were these side effects common, they were also similar to the side effects of whatever drug the patients thought they might be getting: patients getting placebo instead of anticonvulsants, for example, reported memory difficulties, sleepiness, and loss of appetite, while patients getting placebo instead of painkillers got digestive problems, which themselves are commonly caused by painkillers.

This is nothing new. A study in 2006 sat 75 people in front of a rotating drum to make them feel nauseous, and gave them a placebo sugar pill. 25 were told it was a drug that would make the nausea worse: their nausea was worse, and they also exhibited more gastric tachyarrhythmia, the abnormal stomach activity that frequently accompanies nausea.

A paper in 2004 took 600 patients from 3 different specialist drug allergy clinics and gave them either the drug that was causing their adverse reactions, or a dummy pill with no ingredients: 27% of the patients experienced side effects such as itching, malaise and headache from the placebo dummy pill.

And a classic paper from 1987 looked at the impact of listing side effects on the form which patients sign to give consent to treatment. This was a large placebo-controlled trial comparing aspirin against placebo, conducted in three different centres. In two of them, the consent form contained a statement outling various gastrointestinal side effects, and in these centres there was a sixfold increase in the number of people reporting such symptoms and dropping out of the trial, compared with the one centre that did not list such side effects in the form.

This is the amazing world of the nocebo effect, where negative expectations can induce unpleasant symptoms, in the absence of a physical cause. And in any case, it doesn’t help homeopaths: in 2003 Professor Edzard Ernst conducted a systematic review, finding every single homeopathy trial that reported side effects. This systematic search found, in total, 50 episodes of side effects in patients treated with placebo and 63 to patients treated with homoeopathically diluted remedies, with no statistically significant difference in the rates of side effects between the two groups.

The world of the homeopath is reductionist, one-dimensional, and built on the power of the pill: it cannot accommodate the fascinating reality of connections between mind and body which have been elucidated by science. The next time you find yourself trapped at dinner next to some bore who’s decided in middle age that they have secret mystical healing powers, while they earnestly explain how their crass efforts at selling sugar pills represent a meaningful political stand against the crimes of big pharma, just think: some lucky person, somewhere in the world, is sat next to a nocebo researcher.