Study objectives: To evaluate the prevalence of severe insomnia symptoms and the extent to which they are associated with daytime impairments in comorbid mood and anxiety disorders.

Design: Nationally representative cross-sectional survey.

Setting: National Comorbidity Survey-Replication (NCS-R).

Participants: There were 5,692 NCS-R respondents with no mood or anxiety disorder (n = 3,711), mood disorders only (n = 327), anxiety disorders only (n = 1,137), and coexisting mood and anxiety disorders (n = 517).

Interventions: N/A.

Measurements and results: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition disorders and severe insomnia symptoms in the past year were assessed using the World Health Organization (WHO) Composite International Diagnostic Interview. The World Health Organization Disability Assessment Schedule (WHO-DAS) indexed eight domains of daytime impairment in the past 30 days, which included self-care, mobility, cognition, social functioning, time out of role, and four components of productive role functioning. Respondents with comorbid mood and anxiety disorders had significantly higher rates of severe insomnia complaints (42.1-62.8%) relative to the three other groups. Severe insomnia complaints were also significantly more prevalent in individuals with mood (25.2-45.6%) or anxiety disorders only (24.9-45.5%) relative to those with no disorder (12.4-24.3%). Moreover, endorsing a severe insomnia complaint in the past year was associated with increased days of impairment across all past-month WHO-DAS domains for respondents with mood-anxiety comorbidity. For the remaining groups, severe insomnia complaints were related to increased days of impairment across all domains except self-care, and additionally mobility for the group with mood disorders only.

Conclusions: Comorbid mood and anxiety disorders are associated with high rates of severe insomnia complaints, which were independently associated with substantial functional impairment.