The impact of expectancy on the efficacy of acupuncture treatment for postprandial distress syndrome: Secondary analysis of a randomized clinical trial

Background Expectancy is an important source of the placebo effect. However, it is unclear whether this has an effect on the efficacy of acupuncture and sham acupuncture in the treatment of postprandial distress syndrome (PDS). Aim To evaluate the effects of high expectancy (HE) and low expectancy (LE) on the efficacy of acupuncture and sham acupuncture in the treatment of PDS. Methods This post hoc secondary analysis used data from our previous randomized controlled trial. Patients were, respectively, enrolled in the HE group and LE group according to expectancy assessments. The composite primary outcomes were the response rate and the elimination rate after 4 weeks of treatment. Expectancy was considered a factor affecting the efficacy of acupuncture treatment only if both primary outcomes achieved significance. Results For the acupuncture group, the response rate was 84.5% in the HE group and 78.8% in the LE group (p = 0.458), and the elimination rate was 32.1% in the HE group and 21.2% in the LE group (p = 0.241). For the sham acupuncture group, the response rate at week 4 was 52.3% in the HE group and 53.1% in the LE group (p = 0.936), and the elimination rate at week 4 was 23.1% in the HE group and 10.6% in the LE group (p = 0.090). Conclusion In this study, the response rate and elimination rate were higher in the high-expectancy group, but no conclusive evidence was found for an association between expectancy and the efficacy of acupuncture and sham acupuncture.