Estimates of frequency range from 0.2 per 100,000 in Israel to 600 per 100,000 in Japan. These differences may be due to how the studies were conducted or the populations themselves. In the United States,<unk>  is estimated to affect as many as 200,000 Americans, but fewer than 50,000 are diagnosed. The prevalence of<unk>  is about 1 per 2,000 persons.<unk>  is often mistaken for depression, epilepsy, the side effects of medications, poor sleeping habits or recreational drug use, making misdiagnosis likely. While<unk>  symptoms are often confused with depression, there is a link between the two disorders. Research studies have mixed results on co-occurrence of depression in people with<unk> , as the numbers quoted by different studies are anywhere between 6% and 50%.<unk>  can occur in both men and women at any age, although typical symptom onset occurs in adolescence and young adulthood. There is about a ten-year delay in diagnosing<unk>  in adults. Cognitive, educational, occupational, and psychosocial problems associated with the excessive daytime sleepiness of<unk>  have been documented. For these to occur in the crucial teen years when education, development of self-image, and development of occupational choice are taking place is especially devastating. While cognitive impairment does occur, it may only be a reflection of the excessive daytime somnolence.
Narcolepsy
Heart failure
Erotolepsy
Major depressive disorder
Nicotine withdrawal
Anemia
Dancing mania
Sleep apnea