Does expectancy affect insomnia treatment response in cancer survivors receiving acupuncture and cognitive behavioral therapy?

Purpose Insomnia negatively affects quality of life in cancer survivors. Expectations of insomnia treatment efficacy may influence response to intervention. We sought to determine whether pre-treatment outcome expectancy predicts response to two non-pharmacological interventions for insomnia among cancer survivors. Methods We analyzed data from a randomized clinical trial that compared acupuncture versus cognitive behavioral therapy for insomnia (CBT-I) in cancer survivors. Patient expectancy was measured by the Mao Treatment Expectancy Scale (MTES) at baseline. Insomnia severity was assessed using the Insomnia Severity Index (ISI) at treatment completion (week 8). Multivariate linear regression was used to evaluate the associations between pre-treatment expectancy and ISI score at week, 8 adjusting for co-variates. Results Expectancy for acupuncture and CBT-I were similar at baseline (acupuncture: 13.3 +/- 4.0; CBT-I: 13.2 +/- 2.9, p = 0.17). Greater baseline expectancy scores were associated with a greater and statistically significant insomnia severity reduction at week 8 in the acupuncture group (beta coefficients [Coef.] = - 0.35, 95% confidence interval [CI] = - 0.6 to - 0.1, p = 0.016) adjusted for co-variates. Baseline expectancy was not statistically associated with insomnia severity reduction in the CBT-I group (Coef. = - 0.2, 95% CI = - 0.7 to 0.2, p = 0.31). High expectancy was significantly associated with greater proportion of treatment responders at week 8 in the acupuncture group (76% vs. 38%, p = 0.001) but not in the CBT-I group (83% vs. 70%, p = 0.21). Conclusions Higher pre-treatment outcome expectancy predicted significantly greater insomnia improvement in patients receiving acupuncture but not in those receiving CBT-I.