Trajectories of change and long-term outcomes in a randomised controlled trial of internet-based insomnia treatment to prevent depression

Background Insomnia treatment using an internet-based cognitive–behavioural therapy for insomnia (CBT-I) program reduces depression symptoms, anxiety symptoms and suicidal ideation. However, the speed, longevity and consistency of these effects are unknown. Aims To test the following: whether the efficacy of online CBT-I was sustained over 18 months; how rapidly the effects of CBT-I emerged; evidence for distinct trajectories of change in depressive symptoms; and predictors of these trajectories. Method A randomised controlled trial compared the 6-week Sleep Healthy Using the Internet (SHUTi) CBT-I program to an attention control program. Adults (N=1149) with clinical insomnia and subclinical depression symptoms were recruited online from the Australian community. Results Depression, anxiety and insomnia decreased significantly by week 4 of the intervention period and remained significantly lower relative to control for >18 months (between-group Cohen’s d=0.63, 0.47, 0.55, respectively, at 18 months). Effects on suicidal ideation were only short term. Two depression trajectories were identified using growth mixture models: improving (95%) and stable/deteriorating (5%) symptoms. More severe baseline depression, younger age and limited comfort with the internet were associated with reduced odds of improvement. Conclusions Online CBT-I produced rapid and long-term symptom reduction in people with subclinical depressive symptoms, although the initial effect on suicidal ideation was not sustained.This trial was funded by NHMRC project grant 1005867. H.C. is supported by NHMRC fellowship 1056964. P.J.B. is supported by NHMRC fellowship 1083311, and at the time of the study, K.M.G. was supported by NHMRC fellowship 105962