Online insomnia treatment and the reduction of anxiety symptoms as a secondary outcome in a randomised controlled trial: The role of cognitive-behavioural factors

Objective: Insomnia and anxiety commonly co-occur, yet the mechanisms underlying this remain unclear. The current paper describes the impact of an Internet-based intervention for insomnia on anxiety, and explores the influence of two cognitive-behavioural constructs – dysfunctional beliefs about sleep and sleep-threat monitoring. Methods: A large-scale, 9-week, two-arm randomised controlled trial (N = 1149) of community-dwelling Australian adults with insomnia and elevated yet subclinical depression symptoms was conducted, comparing a cognitive behavioural therapy–based online intervention for insomnia (Sleep Healthy Using The Internet) with an attention-matched online control intervention (HealthWatch). Symptoms of anxiety were assessed at pretest, posttest, and 6-month follow-up. Dysfunctional beliefs about sleep and sleep threat monitoring were assessed only at pretest. Results: Sleep Healthy Using The Internet led to a greater reduction in anxiety symptoms at both posttest (t724.27 = –6.77, p