Evaluation and diagnosis of persistent insomnia.

The authors placed 84 patients who complained of insomnia into 10 diagnostic categories on the basis of medical, psychiatric, and polysomnographic evaluations. Only half the patients had objectively defined difficulty inducing or maintaining sleep when compared with 20 normal control subjects. However, all but 16 patients showed polysomnographic evidence of some sleep disorder. Diagnostic categories within the insomnia groups could be distinguished from one another by polysomnography. Patients in only 3 of the 10 diagnostic categories showed evidence of psychological distress on the MMPI; patients in the other 7 categories displayed few psychological symptoms. These results have implications for the treatment of insomnia.