Cognitive behavioural therapy for insomnia for patients with co-morbid generalized anxiety disorder: an open trial on clinical outcomes and putative mechanisms.

Background: Very little is known concerning the efficacy of psychosocial treatments for patients with insomnia disorder co-morbid with generalized anxiety disorder (GAD).

Objective: The aim was to examine the efficacy of cognitive behavioral therapy for insomnia (CBT-I) for patients with insomnia disorder co-morbid with GAD.

Methods: Given the limited, previous research on therapies for patients with insomnia disorder co-morbid with GAD, an open trial design was used. Twenty-four patients with insomnia disorder and GAD were administered CBT-I across 10 weeks. Across the study period to 6 months follow-up, the participants completed measures indexing insomnia, anxiety, worry, depression, functional impairment, quality of life, treatment perception (credibility, expectancy and satisfaction), adverse events and putative mechanisms.

Results: Moderate to large effect sizes for CBT-I were observed for insomnia symptoms. In terms of insomnia severity, approximately 61% of the patients responded to CBT-I and 26-48% remitted. Moderate to large effect sizes were also demonstrated for GAD symptoms, depression, functional impairment and quality of life. Roughly one-third of the participants reported an adverse event during CBT-I. Five of the seven putative mechanisms were significantly reversed in the expected direction, i.e. all four cognitive process measures and time in bed.

Conclusions: This open trial indicates that CBT-I is an efficacious intervention for patients with insomnia disorder co-morbid with GAD. The results highlight the need for further research using a randomized controlled trial design with analyses of mechanisms of change.