Disorders characterized by impairment of the ability to initiate or maintain sleep. This may occur as a primary disorder or in association with another medical or psychiatric condition.

Synonyms: Insomnia, Nonorganic, Insomnia, Secondary, Sleeplessness, Insomnia, Chronic, Insomnia, Rebound, Insomnia Disorders, Insomnia Disorder, Secondary Insomnia, Insomnias, Psychophysiological Insomnia, Dysfunction, Sleep Initiation, Nonorganic Insomnia, Insomnia, Transient, Early Awakening, Chronic Insomnia, Transient Insomnia, Awakening, Early, Sleep Initiation Dysfunctions, Insomnia, Primary, Rebound Insomnia, Sleep Initiation Dysfunction, Disorders of Initiating and Maintaining Sleep, Sleep Initiation and Maintenance Disorders, DIMS (Disorders of Initiating and Maintaining Sleep), Dysfunctions, Sleep Initiation, Insomnia, Psychophysiological, Insomnia, Primary Insomnia