A nightmare, also known as a bad dream, is an unpleasant dream that can cause a strong emotional response from the mind, typically fear but also despair, anxiety or great sadness. However, psychological nomenclature differentiates between nightmares and bad dreams; specifically, people remain asleep during bad dreams, whereas nightmares can awaken individuals. The dream may contain situations of discomfort, psychological or physical terror, or panic. After a nightmare, a person will often awaken in a state of distress and may be unable to return to sleep for a short period of time. Recurrent nightmares may require medical help, as they can interfere with sleeping patterns and cause insomnia. Nightmares can have physical causes such as sleeping in an uncomfortable position or having a fever, or psychological causes such as stress or anxiety. Eating before going to sleep, which triggers an increase in the bodys metabolism and brain activity, can be a potential stimulus for nightmares.The prevalence of nightmares in children (5–12 years old) is between 20 and 30%, and for adults is between 8 and 30%. In common language, the meaning of nightmare has extended as a metaphor to many bad things, such as a bad situation or a scary monster or person. Etymology
The word nightmare is derived from the Old English mare, a mythological demon or goblin who torments others with frightening dreams. The term has no connection with the Modern English word for a female horse. The word nightmare is cognate with the Dutch term nachtmerrie and German Nachtmahr (dated).
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Night-Mares: Demons that Cause Nightmares