Sleep disorders are illnesses related to alterations in the sleep-wake cycle (Table 9-7) and often have effects on mood, cognitive, somatic, and general performance. Table 9-8 outlines the DSM-IV classification of sleep disorders. Sleep disorders are categorized into primary and secondary sleep disorders. Primary sleep disorders are those disorders occurring as a direct result of disturbances in the sleep-wake cycle. They are divided into two categories: dyssomnias and parasomnias. Secondary sleep disorders are a consequence of other mental disorders (e.g., depression) due to general medical conditions (e.g., somatic pain) or substance use (e.g., caffeine).

Dyssomnias
Dyssomnias are five primary sleep disorders consisting of disturbances in initiating and maintaining sleep, feeling rested or refreshed after sleep, or sleeping excessively. Table 9-9 defines the DSM-IV determined key characteristics of each disorder.

Parasomnias
Parasomnias are a triad of sleep disorders associated with complex behavioral events that occur during sleep or that arouse a person from sleep. The disorders are defined in Table 9-9.