Narcolepsy is a long-term neurological disorder that involves a decreased ability to regulate sleep-wake cycles. Symptoms often include periods of excessive daytime sleepiness and brief involuntary sleep episodes. About 70% of those affected also experience episodes of sudden loss of muscle strength, known as cataplexy. These experiences can be brought on by strong emotions. Less commonly, there may be vivid hallucinations or an inability to move (sleep paralysis) while falling asleep or waking up. People with narcolepsy tend to sleep about the same number of hours per day as people without, but...

Hypersomnia is a neurological disorder of excessive time spent sleeping or excessive sleepiness. It can have many possible causes such as seasonal affective disorder and can cause distress and problems with functioning. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), hypersomnolence, of which there are several subtypes, appears under sleep-wake disorders.Hypersomnia is a pathological state characterized by a lack of alertness during the waking episodes of the day. It is not to be confused with fatigue, which is a normal physiological state. Daytime...