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Tuesday, October 26, 2010

Uncontrolled placebo controls

The gold standard for proper medical experiments is the double-blind placebo-controlled study. Beatrice Golomb of the University of California San Diego and her colleagues are arguing that that standard isn’t good enough, if researchers don’t disclose what’s in their placebos.

Placebos, sometimes referred to as ‘sugar pills’, are sham treatments. A good placebo replicates the actual medicine or procedure so closely that no one can tell the difference. For example, a placebo pill should look and taste like the medicinal pill in the study, but not contain any active ingredients. Placebo injections or placebo surgeries must feel like the real things. ‘Double blind’ means that neither the patient nor the doctor knows whether the patient is getting the real treatment or the placebo. It’s actually another level of placebo control, because patients will tend to feel better if their doctor is confident that his treatment will help them.

These careful controls are essential because many people will improve, at least temporarily, from almost any condition even with no treatment. If you give a group of people a medical intervention and many of them improve, you can’t know whether they would have improved anyway unless you have these controls.

The placebo itself is presumed to be inert, meaning that it has no effect. But is it? Golomb and her colleagues found that researchers rarely disclose the exact contents of their placebos. In addition, they argue that placebos themselves haven’t been properly tested to make sure they really don’t have any effect. To take an extreme example, suppose a placebo really were a sugar pill. Couldn’t a dose of sugar have some affect on people suffering from certain conditions? Remember, it’s the comparison to the placebo that tells how effective a drug is. If 60% of patients improve when taking the drug, and 62% improve when taking the placebo, then the drug is deemed ineffective. Therefore, it’s critical to know what if any effect the placebo has on its own.

The authors suggest that in future, researchers take care to disclose the exact contents of their placebos as well as of their treatments. They would also like to see studies done comparing different placebo compositions. Only then will placebo-controlled studies be properly controlled.

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