Does Mid-Treatment Insomnia Severity Mediate between Cognitive Behavioural Therapy for Insomnia and Post-Treatment Depression? An Investigation in a Sample with Comorbid Insomnia and Depressive Symptomatology

• Published in: Behavioural and cognitive psychotherapy 2018-11, Vol.46 (6), p.726-737
• Main Authors: Norell-Clarke, Annika, Tillfors, Maria, Jansson-Fröjmark, Markus, Holländare, Fredrik, Engström, Ingemar
• Format: Article
• Language: English
• Subjects: Behavior modification; Clinical outcomes; Cognition & reasoning; Cognitive ability; Cognitive Behavioral Therapy; Cognitive behavioural therapy; Cognitive therapy; Comorbidity; depression; Depression - complications; Depression - diagnosis; Depression - psychology; Depression - therapy; Depressive Disorder, Major - complications; Depressive Disorder, Major - diagnosis; Depressive Disorder, Major - psychology; Depressive Disorder, Major - therapy; Drug therapy; Female; group psychotherapy; Humans; Insomnia; Male; Mental depression; Middle Aged; Psychiatric Status Rating Scales; Psychology; Psykologi; randomized controlled trial; Research Article; Sleep; Sleep disorders; Sleep Initiation and Maintenance Disorders - complications; Sleep Initiation and Maintenance Disorders - diagnosis; Sleep Initiation and Maintenance Disorders - psychology; Sleep Initiation and Maintenance Disorders - therapy; statistical mediation; Studies; Therapists; Treatment Outcome
• ISSN: 1352-4658; 1469-1833; 1469-1833
• DOI: 10.1017/S1352465818000395

Background: Recent treatment studies with cognitive behavioural therapy for insomnia (CBT-I) have demonstrated effects on both sleep problems and depression. Two previous studies have indicated that the beneficial effect from CBT-I on depression may come through improved sleep, although insomnia severity during treatment had not previously been investigated as a mediator. Aims: Our aim was to investigate if insomnia severity during treatment mediated between CBT-I and depression severity after treatment, in a sample with co-morbid insomnia and depressive symptomology. We also examined whether depressive severity during treatment mediated between CBT-I and insomnia after treatment. Method: The participants were recruited from advertisements and fulfilled criteria for insomnia diagnosis, and had depressive symptomatology (Beck Depression Inventory-second edition: BDI-II > 13). Two-thirds of the participants were diagnosed with major depressive disorder. The participants received four biweekly group sessions of CBT-I or relaxation training (active control). Insomnia severity (Insomnia Severity Index) and depressive severity (BDI-II) were measured at baseline, mid-treatment, post-treatment and 6-month follow-up. The mid-treatment measures were used as mediators. Results: Mediational analyses demonstrated a significant reciprocal relationship between insomnia severity and depressive severity throughout CBT-I, although mid-treatment insomnia had a stronger effect on depression than mid-treatment depression had on insomnia. The results were similar for both post-treatment and follow-up. Discussion: Some improvement in depressive severity after CBT-I is explained by improved sleep. The findings emphasize the importance of making comorbid insomnia a treatment focus in its own right.