What are "night terrors" and why do children get them?

Within fifteen minutes of your daughter's falling asleep, she will probably enter her deepest sleep of the night. This period of slow wave sleep, or deep non-REM sleep, will typically last from forty-five to seventy-five minutes. At this time, most children will transition to a lighter sleep stage or will wake briefly before returning to sleep. Some children, however, get stuck -- unable to completely emerge from slow wave sleep. Caught between stages, these children experience a period of partial arousal.

Partial arousal states are classified in three categories: 1) sleep walking, 2) confusional arousal, and 3) true sleep terrors. These are closely related phenomena that are all part of the same spectrum of behavior.

When most people (including the popular press and popular parenting literature) speak of sleep terrors, they are generally referring to what are called confusional arousals by most pediatric sleep experts (Principles and Practice of Sleep Medicine in the Child, by Ferber and Kryger). Confusional arousals are quite common, taking place in as many as 15% of toddler and pre-school children. They typically occur in the first third of the night on nights when the child is over-tired, or when the sleep-wake schedule has been irregular for several days.

A confusional arousal begins with the child moaning and moving about. It progresses quickly to the child crying out and thrashing wildly. The eyes may be open or closed, and perspiration is common. The child will look confused, upset, or even "possessed" (a description volunteered by many parents). Even if the child does call out her parents' names, she will not recognize them. She will appear to look right through them, unable to see them. Parental attempts to comfort the child by holding or cuddling tend to prolong the situation. Typically a confusional arousal will last for about ten minutes, although it may be as short as one minute, and it is not unusual for the episode to last for a seemingly eternal forty minutes.

During these frightening episodes, the child is not dreaming and typically will have no memory of the event afterwards (unlike a nightmare). If any memory persists, it will be a vague feeling of being chased, or of being trapped. The event itself seems to be a storm of neural emissions in which the child experiences an intense flight or fight sensation. A child usually settles back to quiet sleep without difficulty.

These are very different from nightmares. You won't become aware of your child's nightmares until after she awakens and tells you about them. They are scary dreams that usually occur during the second half of the night, when dreaming is most concentrated. A child may be fearful following a nightmare, but will recognize you and be reassured by your presence. She may have trouble falling back asleep, though, because of her vivid memory of the scary dream.

True sleep terrors are a more intense form of partial arousal. They are considerably less common than confusional arousals, and are seldom described in popular parenting literature. True sleep terrors are primarily a phenomenon of adolescence. They occur in less than 1% of the population.