Impact of Comorbid Anxiety and Depressive Disorders on Treatment Response to Cognitive Behavior Therapy for Insomnia

Objective: To evaluate the impact of comorbid anxiety or depressive disorders on treatment response to cognitive-behavior therapy (CBT) for insomnia, behavior therapy (BT), or cognitive therapy (CT). Method: Participants were 188 adults (117 women; Mage = 47.4 years) with chronic insomnia, including 45 also presenting a comorbid anxiety or mild to moderate depressive disorder. They were randomized to BT (n = 63), CT (n = 65), or CBT (n = 60). Outcome measures were the proportion of treatment responders (decrease of >= 8 points on the Insomnia Severity Index; ISI) and remissions (ISI score <8) and depression and anxiety symptoms. Results: Proportion of treatment responders and remitters in the CBT condition was not significantly different between the subgroups with and without comorbidity. However, the proportion of responders was lower in the comorbidity subgroup compared to those without comorbidity in both the BT (34.4% vs. 81.6%; p = .007) and CT (23.6% vs. 57.6%; p = .02) alone conditions, although remission rates and prepost ISI change scores were not. Pre to post change scores on the depression (-10.6 vs. -3.9; p < .001) and anxiety measures (-9.2 vs. -2.5; p = .01) were significantly greater in the comorbidity subgroup relative to the subgroup without comorbidity but only for those treated with the full CBT; no difference was found for those treated with either BT or CT alone. Conclusions: The presence of a comorbid anxiety or mild to moderate depressive disorder did not reduce the efficacy of CBT for insomnia, but it did for its single BT and CT components when used alone.