A frightening dream that occurs during REM (rapid eye movement) sleep.
Nightmares—frightening dreams—are experienced by most everyone at one time or another. Nightmares are thought to be caused by a central nervous system response, and are related to other parasomnias such as sleepwalking.
In children, nightmares begin between the ages of 18 months and three years and increase in frequency and intensity around the ages of four and five years. Children this age have an exceptionally vivid fantasy life that carries over into their sleep. Their nightmares are typically characterized by feelings of danger and helplessness and often involve fleeing from monsters or wild animals. It is not unusual for a normal child this age to have nightmares as often as once or twice a week. The increase in nightmares among preschoolers reflects not only their capacity for vivid fantasy but also the fact that as they become increasingly active, their daily lives hold more opportunities for frightening experiences, and growing interaction with peers and siblings produces added potential for conflict and tension. Separation anxiety and exposure to frightening programs on television are additional sources of emotional turbulence.
The American Psychiatric Association's Diagnostic and Statistical Manual (DSM-IV) recognizes an anxiety disorder characterized by persistent, severe nightmares (nightmare disorder, formerly dream anxiety disorder). Generally, nightmare disorder is found only in children who have experienced severe psychological stress.
Adults also occasionally experience nightmares. The average college student has between four and eight nightmares per year, and this figure generally drops to one or two in adults. Adults who experience excessive nightmares may be dealing with other issues, and may benefit from professional counseling.