Nightmares

Abstract

Nightmares are reported to occur 2-8% in the general population (American Academy of Sleep Medicine. International classification of sleep disorders, 3rd ed. Darien, IL: American Academy of Sleep Medicine; 2014). While they may be dismissed as "bad dreams," nightmares may be indicative of another disorder occurring in sleep. Nightmares are part of a category of sleep disorders referred to as parasomnias-"undesirable physical events or experiences that occur during entry into sleep, within sleep, or during arousal from sleep" (American Academy of Sleep Medicine. International classification of sleep disorders, 3rd ed. Darien, IL: American Academy of Sleep Medicine; 2014). Parasomnias are categorized by the stage of sleep in which they occur: NREM sleep-typically observed in the first half of the night, versus REM sleep-associated with the latter half of the sleep period. NREM parasomnias are also referred to as "disorders of arousal" and include sleep terrors, sleepwalking, and confusional arousals. REM sleep parasomnias include REM behavior disorder (RBD) and nightmares (dreams with negative content that may cause awakening). It is important to identify what kind of parasomnia the "nightmare" represents, as there may be serious consequences such as injury to ones' self or others that can occur. Additionally, as in the case of RBD, it may be a potential sign of another neurodegenerative process, such as parkinsonism. Polysomnogram is often utilized in the evaluation of parasomnias and can also be helpful to exclude other disorders, which may mimic these conditions.