P093 A Systematic Review of Adherence to Cognitive Behavioural Therapy for Insomnia (CBT-I) - Key Findings

INTRODUCTION: Research into factors influencing adherence to CBT-I and how adherence impacts treatment outcomes remains scarce. Through a systematic review, we aimed to determine how adherence is assessed; which factors predict adherence; and which treatment outcomes are predicted by adherence. METHODS: Included publications met the following criteria: adults with insomnia; an intervention of CBT-I, including sleep restriction (SRT) and/or stimulus control (SCT); a reported measure of adherence; and written in English. RESULTS: Final n=103 papers. Measures assessed either global adherence or adherence to specific components of CBT-I via questionnaires, sleep diaries, interviews, or actigraphy. Most common measures were sleep diary-derived CBT-I components for therapist-led studies, and module completion for digital studies. Twenty-eight papers (27.2% of total) examined predictors of adherence. Depression, pre- and post-session sleep, psychosocial support, and dysfunctional beliefs about sleep predicted adherence. Demographic variables, other psychological comorbidities, insomnia severity, and sleep questionnaires did not predict adherence. Twenty-eight papers (27.2%) examined whether adherence predicted treatment outcomes. Neither global adherence nor adherence to any specific component of therapist-led CBT-I reliably predicted sleep outcomes. For digital CBT-I, completion of treatment modules was linked to improvements in ISI, however there were only five studies. CONCLUSION: There was a high degree of heterogeneity in how adherence was measured, and in predictors and outcome variables assessed. This heterogeneity likely explains why adherence does not appear to predict treatment outcome. The field needs to develop a standardised method for assessing each specific adherence construct to fully understand the role of adherence in CBT-I.