Nightmare disorder is a sleep disorder characterized by repeated or deliberate intense nightmares that most often center on threats to physical safety and security. The nightmares usually occur during the REM stage of sleep, and the person who experiences the nightmares typically remembers them well upon waking. More specifically, nightmare disorder is a type of parasomnia, a subset of sleep disorders categorized by abnormal movement or behavior or verbal actions during sleep or shortly before or after. Other parasomnias include sleepwalking, sleep terrors, bedwetting, and sleep paralysis.
Nightmare disorders can be confused with sleep terror disorders. The difference is that after a sleep terror episode, the patient wakes up with more dramatic symptoms than with a nightmare disorder, such as screaming and crying. Furthermore, they do not remember the reason of the fear, while a patient with a nightmare disorder remembers every detail of the dream. Finally, the sleep terrors usually occur during NREM Sleep.
