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Although insomnia is the most common sleep complaint, the condition frequently is underdiagnosed and undertreated. The lack of an insomnia diagnosis is probably due to the failure to recognize the relationship between psychiatric illness and insomnia.
Sleep disturbance is a part of the diagnostic criteria for many mental disorders, including mood disorders and anxiety disorders. Insomnia also is strongly associated with psychiatric disorders in the general population. On the Minnesota Multiphasic Personality Inventory, 79.3% of the patients with insomnia were positive on at least one clinical scale. The association between insomnia and psychiatric illness is even stronger in the clinical population. A multicenter study found that 75% of patients in sleep clinics or in primary medical clinics could be diagnosed as having psychiatric disorders.
The appropriate diagnosis is crucial for the treatment of presenting symptoms of insomnia, as well as underlying psychiatric disorder. The diagnostic approach for a patient with chronic insomnia includes obtaining a sleep history, a medical history, a psychiatric history, a mental status examination, a physical examination, and a history of substance abuse. Although sleep laboratory testing normally is not included, it should be considered if obstructive sleep apnea or restless legs syndrome is suspected.