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.
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