Parasomnia is a collection of disruptive sleep-related disorders that can occur during arrousals from REM sleep or partial arousals from Non-REM sleep. Parasomnias include nightmares, night terrors, sleepwalking, and many others.


Nightmares are vivid nighttime events that can cause feelings of fear, terror, and/or anxiety. Usually, the person having a nightmare is abruptly awakened from REM sleep and is unable to describe detailed dream content. Usually, the person having a nightmare has difficulty returning to sleep. Nightmares can be caused by many factors including illness, anxiety, the loss of a loved one, or negative reactions to a medication.

Call your doctor if nightmares occur more often than once a week or if nightmares prevent you from getting a good night's sleep for a prolonged period of time.

Night Terrors

Night terrors are episodes of fear, flailing and screaming while asleep. Night terrors often are paired with sleepwalking.

Night terrors differ from nightmares. Whereas the dreamer of a nightmare wakes up from the dream and remembers details, people with night terrors remain asleep. People may recall a dream fragment they had during the night terrors.

A night terror episode usually lasts only a few minutes.

Night terrors are relatively rare. However frightening, night terrors aren't usually a cause for concern. Most people outgrow night terrors by adolescence.


Sleepwalking occurs when a person appears to be awake and moving around but is actually sleeping. They have no memory of their actions. Sleepwalking most often occurs during deem non-REM sleep early in the night and it can occur during REM sleep in the early morning.