Interesting stuff from Ben Goldacre in the Guardian:
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 three 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 outlining 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.