Prevalence of nightmares increases through childhood into adolescence. From 1.3% to 3.9% of parents report that their preschool children have nightmares ”often” or "always”.
Prevalence increases from ages 10 to 13 for both males and females but continues to in- crease to ages 20—29 for females (while decreasing for males), when it can be twice as high for females as for males. Prevalence decreases steadily with age for both sexes, but the gen- der difference remains. Among adults, prevalence of nightmares at least monthly is 6%, whereas prevalence for frequent nightmares is 1%—2%. Estimates often combine idio- pathic and posttraumatic nightmares indiscriminately.
verity in late adolescence or early adulthood. Nightmares most likely appear in children exposed to acute or chronic psychosocial stressors and thus may not resolve spontane- ously. In a minority, frequent nightmares persist into adulthood, becoming virtually a life- long disturbance. Although specific nightmare content may reﬂect the individual’s age, the essential features of the disorder are the same across age groups.
Temperamental. Individuals who experience nightmares report more frequent past ad- verse events, but not necessarily trauma, and often display personality disturbances or psychiatric diagnosis.
Environmental. Sleep deprivation or fragmentation, and irregular sleep-wake schedules that alter the timing, intensity, or quantity of REM sleep, can put individuals at risk for nightmares.
Genetic and physiological. Twin studies have identified genetic effects on the disposi- tion to nightmares and their co-occurrence with other parasomnias (e.g., sleeptalking).
Course modifiers. Adaptive parental bedside behaviors, such as soothing the child fol- lowing nightmares, may protect against developing chronic nightmares.
The significance attributed to nightmares may vary by culture, and sensitivity to such be- liefs may facilitate disclosure.
Adult females report having nightmares more frequently than do adult males. Nightmare content differs by sex, with adult females tending to report themes of sexual harassment or of loved ones disappearing/dying, and adult males tending to report themes of physical aggression or war/terror.
Polysomnographic studies demonstrate abrupt awakenings from REM sleep, usually during the second half of the night, prior to report of a nightmare. Heart, respiratory, and eye move- ment rates may quicken or increase in variability before awakening. N ightmares following traumatic events may also arise during non-REM (NREM), particularly stage 2, sleep. The typ- ical sleep of individuals with nightmares is mildly impaired (e.g., reduced efficiency, less slow- wave sleep, more awakenings), with more frequent periodic leg movements in sleep and rel- ative sympathetic nervous system activation after REM sleep deprivation.
Functional Consequences of Nightmare Disorder pational impairment. However, if awakenings are frequent or result in sleep avoidance, individuals may experience excessive daytime sleepiness, poor concentration, depression, anxiety, or irritability. Frequent childhood nightmares (e.g., several per week), may cause significant distress to parents and child.
Sleep terror disorder. Both nightmare disorder and sleep terror disorder include awak- enings or partial awakenings with fearfulness and autonomic activation, but the two dis- orders are differentiable. Nightmares typically occur later in the night, during REM sleep, and produce vivid, storylike, and clearly recalled dreams; mild autonomic arousal; and complete awakenings. Sleep terrors typically arise in the first third of the night during rate storylike quality. The terrors lead to partial awakenings that leave the individual con— fused, disoriented, and only partially responsive and with substantial autonomic arousal.
There is usually amnesia for the event in the morning.