A mother is awakened in the middle of the night by a terrifying scream. She races to the room of her 3-year-old son. He is sitting up in bed with tears running down his face, his heart pounding. The more she tries to soothe him, the more agitated he becomes.
A college student walks into her parents' bedroom while they are sleeping and pours a glass of water into her mother's dresser drawer.
What these two situations have in common is that, in the morning, they do not remember a thing.
These stories—all true—are examples of parasomnias, which are defined as unpleasant or undesirable behavioral or experiential phenomena during sleep.
Abnormal things that can happen to people while they are sleeping are called parasomnias.
Examples of parasomnias include sleepwalking and night terrors.
While they can be frightening to observe, most parasomnias are harmless and require no treatment beyond some simple safety measures to keep people from injuring themselves during an episode.
Parasomnias are more common in children than in adults because the condition most often occurs during deep sleep, which decreases as we age.
Parasomnias fall into 2 main categories—disorders of REM sleep and non-REM (NREM) sleep.
REM, short for rapid eye movement, sleep is the most active stage of sleep during the second half of the night. This is when most dreams and nightmares occur. During REM sleep, our muscles become relaxed and immobile to keep us from acting out our dreams. In those with REM behavior disorder, the muscles do not relax and people act out their dreams as though awake. Some things that may occur during this time are hitting, punching, or yelling. This disorder can lead to injury of the dreamer or the bed partner. During this time, the dreamer is really asleep.
For most of the night, we are in NREM sleep, which includes the deep sleep. This is when sleepwalking and night terrors occur.
A major difference between the nightmares of REM sleep and the night terrors of NREM sleep is that nightmares involve a complex plot that may be recalled in detail, while the images involved with night terrors are primitive and simplistic, such as fire, a monster, or the ceiling falling down that are not recalled.
Sleepwalking is more prevalent in children than adults. There are many reasons people sleepwalk, but one of them may be hereditary.
During this time, the sleepwalker may be unresponsive and appear awake. Sometimes awakening the sleepwalker can trigger aggression and violent behavior. It is best not to wake the sleepwalker. Try to redirect the person back to bed if possible.
Night terrors differ from nightmares. They occur during non-REM sleep, generally in the first third of the night. They may include incomplete arousal, confusion, unresponsiveness, and amnesia. They can occur in a small minority of children up to 8 years old. Night terrors may also be accompanied by sleepwalking.
Keep in mind that night terrors may render a child inconsolable for several minutes. Once relaxed, the child will often fall back to sleep.
The good news is that most of these things eventually go away on their own. Some people however, need more involved treatment. This may include educating family members on how to respond to parasomnias, relaxation therapy, and, rarely, medication.
You can help prevent parasomnias by having your child keep the same sleep schedule and get enough sleep. This will prevent the increase in deep sleep that can trigger sleepwalking, night terrors, and other parasomnias.
There are some general safety precautions you can take if you or someone you know experiences parasomnias:
If your child has frequent nightmares, night terrors, or sleepwalks, contact your child's pediatrician for additional advice.
National Heart, Lung, and Blood Institute
National Sleep Foundation
Better Sleep Council Canada
Bruni O, Novelli L. Sleep disorders in children. Clin Evid (Online). 2010; 2010:2304.
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Nightmares and sleep. National Sleep Foundation website. Available at: http://www.sleepfoundation.org/article/sleep-related-problems/nightmares-and-sleep. Accessed January 2, 2015.
Parasomnias. National Heart Blood Lung Institute website. Available at: http://www.sleepfoundation.org/article/ask-the-expert/sleep-and-parasomnias. Accessed January 2, 2015.
Sleep and parasomnias. National Sleep Foundation website. Available at: http://www.sleepfoundation.org/article/ask-the-expert/sleep-and-parasomnias. Accessed January 2, 2015.
Sleepwalking. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated May 13, 2014. Accessed January 2, 2015.
What happens when you sleep? National Sleep Foundation website. Available at: http://www.sleepfoundation.org/article/how-sleep-works/what-happens-when-you-sleep. Accessed January 2, 2015.
Last reviewed January 2015 by Michael Woods, MD