Nightmares
The word nightmare is derived from the Old English mare, a mythological demon or goblin who torments others with frightening dreams. Originally, "mare" or "nightmare" referred more specifically to sleep paralysis, in which an experience of terror and paralysis during sleep can be associated with a sense of pressure on the chest and the dreamed presence of entities often pictured as demons, sometimes sitting on the chest.
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The meaning of "nightmare" had generalized from sleep paralysis to any bad dream by 1829.[1] In other languages, the word for "bad dream" similarly evolved in sense from words for "sleep paralysis," often with senses related to the pressure on the chest.
Signs and Symptoms
Those with nightmares experience abnormal sleep architecture. The impact of having a nightmare during the night has been found to be very similar to that of insomnia. This is thought to be caused by frequent nocturnal awakenings and fear of falling asleep.[8] When awoken from REM sleep by a nightmare, the dreamer can usually recall the nightmare in detail. They may also awaken in a heightened state of distress, with an elevated heart rate or increased perspiration.[9] Nightmare disorder symptoms include repeated awakenings from the major sleep period or naps with detailed recall of extended and extremely frightening dreams, usually involving threats to survival, security, or self-esteem. The awakenings generally occur during the second half of the sleep period.
Causes
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 body's metabolism and brain activity, can be a potential stimulus for nightmares.
According to the International Classification of Sleep Disorders-Third Edition (ICSD-3), the nightmare disorder, together with REM sleep behaviour disorder (RBD) and recurrent isolated sleep paralysis, form the REM-related parasomnias subcategory of the Parasomnias cluster.[11] Nightmares may be idiopathic without any signs of psychopathology or associated with disorders like stress, anxiety, substance abuse, psychiatric illness or PTSD (>80% of PTSD patients report nightmares).[12] As regarding the dream content of the dreams they are usually imprinting negative emotions like sadness, fear or rage.
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