Night terrors typically occur in children ages 3-12, with a peak onset at age 3 1/2. Sleep is divided into two categories: rapid eye movement (REM) and non-rapid eye movement (non-REM). Non-REM sleep is further divided into four stages, progressing from stages 1-4. Night terrors occur during the transition from stage 3 non-REM sleep to stage 4 non-REM sleep, beginning approximately 90 minutes after the child falls asleep.
Night terrors are distinctly different from common nightmares, which occur during REM sleep. Night terrors are characterized by frequent recurrent episodes of intense crying and fear during sleep, with difficulty arousing the child. Night terrors are frightening episodes that can disrupt family life.
An estimated 1-6 percent of children experience night terrors. Boys and girls are equally affected. Children of all races also seem to be affected equally.