Duration of insomnia and success expectancy predict treatment outcome of iCBT for insomnia

Abstract

Introduction: Identifying prognostic factors of treatment outcome may assist in customizing an intervention to a patient's needs. Hence, we conducted a secondary analysis of data from a randomized controlled trial to investigate the effectiveness of an internet-based cognitive behavioral therapy for insomnia (iCBT-I) to find patient characteristics that may predict the change of insomnia severity after treatment. Materials and methods: In this exploratory analysis involving 94 chronic insomnia patients, we examined the predictive value of several self-reported measures, medical history, and sociodemographic variables to psychological distress with separate linear regression models. The main outcome was the Insomnia Severity Index score improvement from pre- to post-treatment Results: The study found that duration of insomnia, b (SE) = −0.02 (0.01), p = 0.01, and attitudes about the expected treatment success, b (SE) = 0.80 (0.27), p = 0.004, were predictors of a better outcome. Moreover, a better outcome was associated with a lower level of the following traits: attention seeking, b (SE) = −1.06 (0.51), p = 0.04; grandiosity, b (SE) = −1.50 (0.57), p = 0.01; distractibility, b (SE) = −1.57 (0.75), p = 0.04; and rigid perfectionism, b (SE) = −1.32 (0.65), p = 0.05. Conclusion: Our results suggest that iCBT-I might be particularly beneficial for patients with higher expectations from the therapy and those who have a shorter duration of insomnia. Some pronounced personality traits, such as attention seeking, grandiosity, distractibility, and rigid perfectionism, may predict worse outcomes. However, because this was a post-hoc analysis, our results must be considered exploratory and verified in further studies. Clinical trial registration: https://clinicaltrials.gov/study/NCT04300218?cond=NCT04300218&rank=1, Identifier NCT04300218.