2011

The term placebo effect refers to the changes in an individual caused by placebo manipulation (Koshi & Short, 2007). In clinical trials, substances or procedures designed to serve as control conditions may actually produce an effect on subjective or biomarker outcomes. Stewart-Williams and Podd (2004) provide a definition for placebo that states “A placebo is a substance or procedure that has no inherent power to produce an effect that is sought or expected” (pp. 326). They also define the placebo effect as “a genuine psychological or physiological effect, in a human or another animal, which is attributable to receiving a substance or undergoing a procedure, but is not due to the inherent powers of that substance or procedure” (pp. 326). These indirect effects of inactive procedures are considered under the umbrella term placebo effects (Kaptchuk, 1998; Oken, 2008).