To Örebro University

Introduction: Insomnia and depression is a common comorbidity and several pilot studies have demonstrated promising results on both conditions by targeting insomnia only. The aim was to investigate the effects of CBT for insomnia (CBT-I) on both sleep and depressive symptoms in a sample with insomnia comorbid with major depression, minor depression or depressive symptoms, using a randomized controlled study.

Materials and methods: 64 participants were recruited through advertisements and randomised to receive either CBT-I or an active control (relaxation training: RT) in groups during four sessions over seven weeks. Insomnia and depressive severity was measured before, during and after treatment, using Insomnia Severity Index (ISI) and Beck Depression Inventory (BDI- II).

Results: We used independent t-tests to investigate if groups were different on symptom severity prior to treatment. There was no difference between CBT-I and RT regarding insomnia severity (t (55) = 1.30, p = 0.20) or depression severity (t (53) = −0.77, p = 0.44). Looking at development over time, mixed between-within subjects ANOVAs demonstrated a significant interaction between treatment type and time for both insomnia and depression (ISI: F (2, 54) = 4.96, p = 0.01; BDI: F (2, 58) = 2.80, p = 0.07) meaning that CBT-I meant a larger decrease of both insomnia and depressive severity compared to control treatment. There was also a significant main effect for time with decreasing scores for both groups over time on ISI (F (2, 52) = 28.86, p = 0.0005) and BDI-II (F (2, 58) = 7.11, p = 0.002) and a main effect for group on ISI (F (1, 53) = 9.25, p = 0.01) but not on BDI-II (F (1, 59) = 0.27, p = 0.60). A six months follow-up assessment is currently conducted and those results will also be presented during the conference.

Conclusion: CBT-I was associated with a greater reduction in insomnia and depression severity compared to control treatment. These results show that it is possible to have an effect on both insomnia and depression during a relatively short and cost effective group treatment, targeting insomnia only.