A new study underlines the importance of explaining placebos more thoroughly.
To find out whether a drug or medical intervention works, researchers must pit it against a placebo.
If the experimental condition cannot outperform the placebo, then they cannot consider it to be effective.
However, a recent study explains how placebos are not as benign as many people believe.
The researchers behind the new study ask whether scientists take the time to explain the exact formulations of their placebo treatments when publishing their results.
Placebos come in many forms, including saline injections, sham surgery, and tablets or capsules of any shape, size, or color.
They also contain a range of ingredients, sometimes including a chemical to mimic the taste or feel of the active drug. As the authors of the new study explain, "[a]ll of these differences can influence how effective they are."
Problems with placebos
The authors outline an example where a particular placebo skewed the results of several studies. In studies that investigated oseltamivir, which people may know by its brand name Tamiflu, scientists often added dehydrocholic acid to the placebo.
Dehydrocholic acid has a bitter taste, as does oseltamivir. The researchers chose to add this chemical to the placebo so that the participants would not know whether they had received the active drug or the placebo.
However, both dehydrocholic acid and oseltamivir cause gastrointestinal side effects. When scientists attempted to calculate the rate of gastrointestinal side effects due to oseltamivir, they compared them with side effects from the placebo.
As the placebo also caused these types of symptoms, scientists underestimated the overall gastrointestinal side effect rate for oseltamivir.
Another issue is mismatching between a placebo and the experimental condition — in other words, they do not look, taste, or feel the same. In these cases, a participant can easily determine that they are not receiving the experimental drug.