The role of polysomnography in the differential diagnosis of chronic insomnia

Abstract
The authors examined the accuracy of the differential diagnosis of chronic insomnia with and without sleep laboratory studies in a consecutive series of 123 patients. All patients were evaluated by means of a sleep/wake log, a sleep habits questionnaire, structured psychiatric and clinical interviews, and a minimum of two consecutive nights of polysomnography. Notwithstanding a high rate of Research Diagnostic Criteria (RDC)-diagnosed psychopathology (63%) in this sample, the major finding was that in 49% of the patients laboratory results added to, refuted, and/or failed to support the clinical impression. This resulted in substantial modification of the initial diagnostic formulation and therefore in increased specificity of diagnosis.