Sleep terrors often runs in families. They occur during partial arousal from stage 4 sleep in which the sleeper does not come to full consciousness. There is usually no memory of the episode the following day.

Most cases begin in childhood and are attributed mainly to delayed development of the nervous system, and the child usually grows out of it by adolescence. They usually begins with a scream. The sleeper springs up in a state of panic—eyes open, perspiring, breathing rapidly, and their heart beating two to three times faster than usual. Episodes usually last between 5 and 15 minutes. After the episode the person falls back asleep.

If not awakened during a night terror, children usually have no memory of the episode. If awakened they possibly will remember a single frightening image.

Sleep terrors in young children should not cause too much concern on the part of the parents. Episodes that continue through adolescence and adulthood are more serious. In adults sleep terrors often indicate extreme anxiety or other psychological problems. Up to 5% of children experience sleep terrors. Only about 1% of adults experience sleep terrors