Nightmare

Nightmare
The Sleep of Reason Produces Monsters (Francisco de Goya, c.1797)
Classification and external resources
ICD-10	F51.5
ICD-9-CM	xxx
[]

A nightmare, also called a bad dream, is an unpleasant dream that can cause a strong emotional response from the mind, typically fear but also despair, anxiety and great sadness. The dream may contain situations of discomfort, psychological or physical terror or panic. Sufferers often awaken in a state of distress and may be unable to return to sleep for a small period.

Nightmares can have physical causes such as sleeping in an uncomfortable or awkward position, having a fever, or psychological causes such as stress, anxiety, and as a side effect of various drugs. Eating before going to sleep, which triggers an increase in the body's metabolism and brain activity, is a potential stimulus for nightmares.

Recurrent nightmares may require medical help, as they can interfere with sleeping patterns and cause insomnia.

The word "nightmare" is derived from the Old English "mare", a mythological demon or goblin who torments others with frightening dreams. Subsequently, the prefix "night-" was added to stress the dream aspect. The word "nightmare" is cognate with the older Dutch term nachtmerrie and German Nachtmahr.

Fearfulness in waking life is correlated with the incidence of nightmares. Studies of dreams have estimated that about 75% of the time, the emotions evoked by dreams are negative. However, it is worth noting that people are more likely to remember unpleasant dreams.

One definition of "nightmare" is a dream which causes one to wake up in the middle of the sleep cycle and experience a negative emotion, such as fear. This type of event occurs on average once per month. They are not common in children under five, but they are more common in young children (25% experiencing a nightmare at least once per week), most common in teenagers, and common in adults (dropping in frequency about one third from age 25 to 55).

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