Nightmare Disorders

Abstract

Nightmares are a relatively prevalent parasomnia, associated with a range of psychiatric conditions and pathological symptoms (Nielsen and Levin 2007). They also occur at times of overall heightened arousal in otherwise healthy individuals. Nightmares are more frequent during childhood where they, not unlike other childhood parasomnias, probably represent a benign disorder caused by immaturity of neural circuits (Nevsimalova et al. 2013). Current knowledge about how nightmares are produced is still influenced by neo-psychoanalytic speculations, as well as by more recent personality, evolutionary and neurobiological models (Nielsen and Levin 2007). A majority of these models stipulate some type of emotionally adaptive function for dreaming, including image contextualization, affect desomatization, mood regulation or fear extinction (Nielsen and Levin 2007). It is generally accepted that dreams likely represent a state of consciousness, characterized by internally generated sensory, cognitive and emotional experiences occurring during sleep (Desseilles et al. 2011). Even normal dream reports tend to be abundant, with complex, emotional and perceptually vivid experiences after awakening from rapid eye movement (REM) sleep (Desseilles et al. 2011) or less often also during the non-REM (nREM) sleep. Emotional experiences in most dreams, not just nightmares, are frequent, intense and possibly biased towards negative emotions. Nightmares, on the other hand, can represent an intensified expression of an emotionally adaptive function, or, conversely, they can be taken as evidence of its breakdown (Nielsen and Levin 2007). One such example is highly emotionally loaded dreams and nightmares in post-traumatic stress disorder (PTSD) which can disrupt the maintenance of REM sleep (Nielsen and Levin 2007).