Transdiagnostic CBT-I on Comorbid Depression and Insomnia

This randomized control trial (RCT) aims at comparing the efficacy of self-help cognitive behavioural therapy for insomnia (CBT-I) and self-help cognitive behavioural therapy for depression (CBT-D) on comorbid depression and insomnia. It addresses the research gap of treating comorbid depression and insomnia with a transdiagnostic approach (i.e., CBT-I) rather than a disorder-specific approach (i.e., CBT-D). Insomnia is a transdiagnostic process that is common to many psychiatric disorders. It is not only a symptom for depression, but also a factor that contributes to the onset and maintenance of depression. There were limited studies comparing the efficacy of self-help CBT-I to self-help CBT-D among adults with comorbid insomnia and depression (e.g., Blom, 2015). Hence, this study will serve as one of the pioneering attempts to elucidate the role of self-help transdiagnostic insomnia therapy in reducing depressive symptoms. Prior to all study procedures, eligible participants will be required to complete an online informed consent. Around 100 eligible participants aged between 18 and 65 with a Patient Health Questionnaire-9 score ≥ 10 indicating at least moderate level of depressive symptoms and Insomnia Severity Index (ISI) score ≥ 10 indicating clinical level of insomnia symptoms will be randomly assigned to either Internet-based CBT-I (n = 50) or Internet-based CBT-D (n = 50) in a ratio of 1:1. Eligible participants in the CBT-I group will receive the intervention "iSleepWell" via the a digital mental health platform Next Stop, Wellness! for 6 consecutive weeks, whilst the CBT-D group will receive the intervention 'LIFE FLeX' via the same platform for 6 consecutive weeks. The outcomes of interest include depressive, anxiety, and insomnia symptoms, functional impairment, quality of life, intervention credibility and acceptability at baseline (Week 0), immediate post-treatment (Week 7), and 12 weeks follow-up (Week 19) assessments.