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Nature Reviews Drug Discovery 7, 554 (1 July 2008) | doi:10.1038/nrd2629

Ted Kaptchuk

box What is the placebo effect and what is the importance of understanding it? The simplest answer is that the placebo effect is the changes we detect in the placebo arm of a randomized controlled trial (RCT). That definition is historically accurate because we did not have a placebo effect until we had an RCT and were then able to see that people who were given inert substances improved.