Expectancy Effect in Three Mind-Body Clinical Trials

摘要

Expectancy, arguably the prime component of the placebo effect, has been shown to significantly modify the effects of many treatments. Furthermore, various forms of mind-body interventions have demonstrated effective improvements in outcomes. The aim of this study was to examine the relationship between pretreatment expectations and symptom reduction in a secondary analysis of 3 mind-body intervention programs. An adjusted correlation and regression analysis compared data from a 6-question expectancy questionnaire to a self-reported clinical impression of change score. Only 1 of the 6 expectancy questions in 1 of the 3 studies reached significance (B = 0.087; P =.025). The combined data from all 3 studies did not reveal significant expectancy effects. The positive effects of mindfulness meditation appear to be independent of an expectancy effect.