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SCHLAFLÄHMUNG

[noun]

sleep paralysis - a phenomenon in which people, either when falling asleep or wakening, temporarily experience an inability to move. More formally, it is a transition state between wakefulness and rest characterised by complete muscle atonia (muscle weakness). It can occur at sleep onset or upon awakening, and it is often associated with terrifying visions (e.g. an intruder in the room), to which one is unable to react due to paralysis. Sleep paralysis has been linked to disorders such as narcolepsy, migraines, anxiety disorders, and obstructive sleep apnea; however, it can also occur in isolation. When linked to another disorder, sleep paralysis commonly occurs in association with the neuromuscular disorder narcolepsy.

Some features of sleep paralysis:

- Eye movements are typically preserved. It more often occurs while sleeping on one’s back.

- Visual and auditory hallucinations often occur and may include a sense of an evil presence, of being touched, or hearing voices or noises in the room.

- Occasionally faces or people may be seen at the bedside.

- A sense of breathlessness (or chest pressure, even someone standing on one’s chest) may exist.

It is common and may be experienced by 20% to 60% of people, depending on the population examined. In a study of college students, 21% were found to have had at least one episode of sleep paralysis, but only 4% had 5 or more episodes. It is believed to be precipitated by sleep deprivation, stress, and sleep schedule disruption. In experiments, it has been shown to occur with disruption of rapid eye movement (REM), or dream sleep. 

Etymology: German Schlaf, “sleep” + Lähmung “paralysis” (from lähmen, “paralysis” and ung, suffix forming nouns from verbs).