There are two main characteristics of<unk> : excessive daytime sleepiness and abnormal REM sleep. Excessive daytime sleepiness occurs even after adequate night time sleep. A person with<unk>  is likely to become drowsy or fall asleep, often at inappropriate or undesired times and places, or just be very tired throughout the day. Narcoleptics may not be able to experience the amount of restorative deep sleep that healthy people experience due to abnormal REM regulation – they are not "over-sleeping". Narcoleptics typically have higher REM sleep density than non-narcoleptics, but also experience more REM sleep without atonia. Many narcoleptics have sufficient REM sleep, but do not feel refreshed or alert throughout the day. This can feel like living their entire lives in a constant state of sleep deprivation. Excessive sleepiness can vary in severity, and it appears most commonly during monotonous situations that don't require much interaction. Daytime naps may occur with little warning and may be physically irresistible. These naps can occur several times a day. They are typically refreshing, but only for a few hours or less. Vivid dreams may be experienced on a regular basis, even during very brief naps. Drowsiness may persist for prolonged periods or remain constant. In addition, night-time sleep may be fragmented, with frequent awakenings. A second prominent symptom of<unk>  is abnormal REM sleep. Narcoleptics are unique in that they enter into the REM phase of sleep in the beginnings of sleep, even when sleeping during the day. The classic symptoms of the disorder, often referred to as the "tetrad of<unk> ," are cataplexy, sleep paralysis, hypnagogic hallucinations, and excessive daytime sleepiness. Other symptoms may include automatic behaviors and night-time wakefulness. These symptoms may not occur in all people with<unk> . * Cataplexy is an episodic loss of muscle function, ranging from slight weakness such as limpness at the neck or knees, sagging facial muscles, weakness at the knees often referred to as "knee buckling", or inability to speak clearly, to a complete body collapse. Episodes may be triggered by sudden emotional reactions such as laughter, anger, surprise, or fear. The person remains conscious throughout the episode. In some cases, cataplexy may resemble epileptic seizures. Usually speech is slurred and vision is impaired (double vision, inability to focus), but hearing and awareness remain normal. Cataplexy also has a severe emotional impact on narcoleptics, as it can cause extreme anxiety, fear, and avoidance of people or situations that might elicit an attack. Cataplexy is generally considered to be unique to<unk>  and is analogous to sleep paralysis in that the usually protective paralysis mechanism occurring during sleep is inappropriately activated. The opposite of this situation (failure to activate this protective paralysis) occurs in rapid eye movement behavior disorder. * Periods of wakefulness at night *Sleep paralysis is the temporary inability to talk or move when waking (or less often, when falling asleep). It may last a few seconds to minutes. This is often frightening but is not dangerous. *Hypnagogic hallucinations are vivid, often frightening, dreamlike experiences that occur while dozing or falling asleep. Hypnopompic hallucinations refer to the same sensations while awakening from sleep. These hallucinations may manifest in the form of visual or auditory sensations. In most cases, the first symptom of<unk>  to appear is excessive and overwhelming daytime sleepiness. The other symptoms may begin alone or in combination months or years after the onset of the daytime naps. There are wide variations in the development, severity, and order of appearance of cataplexy, sleep paralysis, and hypnagogic hallucinations in individuals. Only about 20 to 25 percent of people with<unk>  experience all four symptoms. The excessive daytime sleepiness generally persists throughout life, but sleep paralysis and hypnagogic hallucinations may not. Many people with<unk>  also suffer from insomnia for extended periods of time. The excessive daytime sleepiness and cataplexy often become severe enough to cause serious problems in a person's social, personal, and professional life. Normally, when an individual is awake, brain waves show a regular rhythm. When a person first falls asleep, the brain waves become slower and less regular, which is called non-rapid eye movement (NREM) sleep. After about an hour and a half of NREM sleep, the brain waves begin to show a more active pattern again, called REM sleep (rapid eye movement sleep), when most remembered dreaming occurs. Associated with the EEG-observed waves during REM sleep, muscle atonia is present called REM atonia. In<unk> , the order and length of NREM and REM sleep periods are disturbed, with REM sleep occurring at sleep onset instead of after a period of NREM sleep. Also, some aspects of REM sleep that normally occur only during sleep, like lack of muscular control, sleep paralysis, and vivid dreams, occur at other times in people with<unk> . For example, the lack of muscular control can occur during wakefulness in a cataplexy episode; it is said that there is an intrusion of REM atonia during wakefulness. Sleep paralysis and vivid dreams can occur while falling asleep or waking up. Simply put, the brain does not pass through the normal stages of dozing and deep sleep but goes directly into (and out of) rapid eye movement (REM) sleep. As a consequence night time sleep does not include as much deep sleep, so the brain tries to "catch up" during the day, hence excessive daytime sleepiness. People with<unk>  may visibly fall asleep at unpredicted moments (such motions as head bobbing are common). People with<unk>  fall quickly into what appears to be very deep sleep, and they wake up suddenly and can be disoriented when they do (dizziness is a common occurrence). They have very vivid dreams, which they often remember in great detail. People with<unk>  may dream even when they only fall asleep for a few seconds. Along with vivid dreaming, people with<unk>  are known to have audio or visual hallucinations prior to falling asleep. Narcoleptics can gain excess weight; children can gain 20 to 40 lb (9 to 18 kg) when they first develop<unk> ; in adults the body-mass index is about 15% above average.
Narcolepsy
Heart failure
Erotolepsy
Major depressive disorder
Nicotine withdrawal
Anemia
Dancing mania
Sleep apnea