| Disorder | Clinical features | Diagnosis | |
| Insufficient nocturnal sleep | Inadequate sleep hygiene | Inconsistent bedtime and morning wake-up times; abuse of caffeine, alcohol, nicotine, or an illicit substance; use of electronic media around bedtime or at night | Detailed history about sleep-wake schedules and habits; sleep logs, actigraphy and urine drug screen |
| Delayed sleep-wake phase disorder | Teenager with inability to fall asleep prior to midnight to 2:00 AM, relatively well-organized and normal sleep quality, inability to awaken fully prior to mid-morning; male predominance | Actigraphy and sleep logs show characteristic delayed sleep onset and offset times | |
| Fragmented nocturnal sleep | Obstructive sleep apnea | Habitual snoring, mouth breathing, daytime sleepiness, obesity, narrow nasal passages or oropharynx | PSG: obstructive apneas and hypopneas, oxygen desaturations associated with apneas |
| Other central disorders of hypersomnolence | Idiopathic hypersomnia | Chronic hypersomnolence with onset in the teenage years, slightly more common in females, relatively normal nocturnal sleep architecture | PSG: relatively normal sleep architecture, without sleep-disordered breathing or sleep-onset REM periods MSLT: shortened mean sleep latency (≤8 minutes), but absence of two or more sleep-onset REM periods |
| Kleine-Levin syndrome | Teenager with periods of hypersomnia lasting 10 to 14 days and occurring 2 to 3 times per year; normal sleep-wake function in intervening periods; male predominance; hyperphagia, anorexia, feelings of depersonalization | Clinical diagnosis. There are no reliable PSG or MSLT findings, although suppression of N3 sleep and increased sleep fragmentation may be seen in some cases in the early stages | |
| Psychiatric disorders | Depression | Daytime somnolence and fatigue, apathy, may have anorexia or increased appetite, mood disturbance, suicidal ideation, and disrupted nocturnal sleep | Clinical diagnosis |
