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 (t _724.27 = –6.77, p < 0.001) and at 6-month follow-up (t _700.67 = –4.27, p < 0.001) than HealthWatch. At posttest and follow-up, this effect was found to moderated by sleep-threat monitoring (t _713.69 = –2.39, p < 0.05 and t _694.77 = –2.98, p < 0.01 respectively) but not by dysfunctional beliefs about sleep at either posttest or follow-up (t _717.53 = –0.61, p = 0.55 and t _683.79 = 0.22, p = 0.83 respectively). Participants in the Sleep Healthy Using The Internet condition with higher levels of sleep-threat monitoring showed a greater reduction in anxiety than those with lower levels from pretest to posttest, (t _724.27 = –6.77, p < 0.001) and through to 6-month follow-up (t _700.67 = –4.27, p < 0.001). This result remained after controlling for baseline anxiety levels. Conclusion: The findings suggest that online cognitive behavioral therapy interventions for insomnia are beneficial for reducing anxiety regardless of people’s beliefs about their sleep and insomnia, and this is particularly the case for those with high sleep-threat monitoring. This study also provides further evidence for cognitive models of insomnia.