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By Laura E. Gibson, Ph.D., University of Vermont

What are nightmares?

Nightmares refer to complex dreams that cause high levels of anxiety or terror. In general, the content of nightmares revolves around imminent harm being caused to the individual (e.g., being chased, threatened, injured, etc.). When nightmares occur as a part of posttraumatic stress disorder (PTSD), they tend to involve the original threatening or horrifying set of circumstances that was involved during the traumatic event. For example, someone who was in the Twin Towers on Sept. 11, 2001, might experience frightening dreams about terrorists, airplane crashes, collapsing buildings, fires, people jumping from buildings, etc. A rape survivor might experience disturbing dreams about the rape itself or some aspect of the experience that was particularly frightening (e.g., being held at knifepoint).

Nightmares can occur multiple times in a given night, or one might experience them very rarely. Individuals may experience the same dream repeatedly, or they may experience different dreams with a similar theme. When individuals awaken from nightmares, they can typically remember them in detail. Upon awakening from a nightmare, individuals typically report feelings of alertness, fear, and anxiety. Nightmares occur almost exclusively during rapid eye movement (REM) sleep. Although REM sleep occurs on and off throughout the night, REM sleep periods become longer and dreaming tends to become more intense in the second half of the night. As a result, nightmares are more likely to occur during this time.

How common are nightmares?

The prevalence of nightmares varies by age group and by gender. Nightmares are reportedly first experienced between the ages of 3 and 6 years. From 10% to 50% of children between the ages of 3 and 5 have nightmares that are severe enough to cause their parents concern. This does not mean that children with nightmares necessarily have a psychological disorder. In fact, children who develop nightmares in the absence of traumatic events typically grow out of them as they get older. Approximately 50% of adults report having at least an occasional nightmare. Estimates suggest that between 6.9% and 8.1% of the adult population suffer from chronic nightmares.

Women report having nightmares more often than men do. Women report two to four nightmares for every one nightmare reported by men. It is unclear at this point whether men and women actually experience different rates of nightmares, or whether women are simply more likely to report them.