Prevalence and Clinical Correlates of Insomnia in Depressive Disorders: The CRESCEND Study.

Objective: To investigate the prevalence, clinical manifestations, and clinical correlates of insomnia in a large cohort of Korean patients with depressive disorders.

Methods: We recruited 944 patients with depressive disorders from the Clinical Research Center for Depression of South Korea (CRESCEND) study. Psychometric scales were used to assess depression (HAMD), anxiety (HAMA), psychotic symptoms (BPRS), global severity (CGI-S), and functioning (SOFAS). Insomnia levels were determined by adding the scores for all items on the HAMD insomnia subscale. The clinical characteristics of the patients with 'low insomnia' (summed score ≤3 on the HAMD subscale) and 'high insomnia' (score ≥4) were compared using statistical analyses. A logistic regression model was constructed to identify factors associated with 'high insomnia' status.

Results: Symptoms of insomnia were present in 93% of patients, while simultaneous early, middle, and late insomnia affected 64.1%. The high insomnia patients were characterized by significantly greater age, higher symptom levels (including core, gastrointestinal somatic and anxiety symptoms, and suicidal ideation), higher global severity and incidence of physical disorders, and greater insight. Explanatory factors of 'high insomnia' status were older age, higher gastrointestinal somatic and anxiety symptom levels, higher global severity, and greater insight.

Conclusion: In clinical psychiatry, insomnia has been significantly underdiagnosed and undertreated. It affects most patients with depressive disorders, and is indicative of the global severity of depression. Active efforts to diagnose and treat insomnia in patients with depressive disorders should be strongly encouraged. Further research is needed to improve the diagnosis and treatment of insomnia in depressive patients.