Placebo-controlled clinical trials are the gold standard of medical research. When doctors and other researchers want to know if a potential new drug is actually effective in treating disease, they design a controlled clinical trial comparing the drug to an ostensibly inert placebo. As I wrote last year, it’s critical to compare the drug to placebo, because otherwise it’s impossible to know whether the patients would have gotten better (or worse) anyways. Patients who believe their illness is being treated will often improve faster than those who are not confident that the treatment (or lack thereof) is actually helping. This is the placebo effect, and it’s a cornerstone of modern medicine. True placebos don’t have any power to treat disease; they just allow us to compare a proposed treatment to a neutral alternative.
But what if the placebo itself isn’t actually neutral? What if, for example, patients were allergic to some ingredient in a placebo? Might researchers be led into believing that the proposed treatment is more effective than it really is, since the placebo they’re comparing it to actually harms some patients?
You might argue that if this was the case, it would be a simple matter to take a look at the contents of placebos in a field of research and assess their potential side effects. Unfortunately, last week, UK medical writer Helen Jaques examined a recently published report suggesting that investigating the composition of placebos would not be a simple matter. A team led by Beatrice Golumb reviewed 176 clinical trials published in four highly-regarded medical journals in 2008 and 2009 and found that surprisingly few reports disclosed the contents of placebos used in the research. Only 23 percent of the trials gave full reports of the makeup of the placebos they used, and even counting partial reports, the number only increased to 32 percent. Studies involving pills (as opposed to shots or other treatments) disclosed even less: Just 9.3 percent of trials of pills gave full descriptions of the placebos used. The investigative report was published in Annals of Internal Medicine.