The normal sleep cycle involves distinct stages from light drowsiness to deep sleep. During REM (rapid eye movement) sleep, the eyes move rapidly and vivid dreaming is most common. Each night there are several cycles of non-REM and REM sleep. Night terror (sleep terror) occurs during Stage 3 and Stage 4 sleep (deep sleep). The cause is unknown but night terrors are commonly associated with periods of emotional tension, stress, or conflict. Night terror is similar to nightmares except that nightmares usually occur during REM sleep and include unpleasant or frightening dreams. Nightmares are most common in the early morning. Night terrors occur usually in the first half of the night heralded by a scream. The child does not usually remember the details of the scare. Nightmares are normal on occasion, especially after frightening movies/TV shows or emotional situations. Night terror occurs most often in preadolescent boys, although it can occur in girls and in adults. It is fairly common in children 3 to 5 years old, and much less common after that. Night terror may run in families. It can occur in adults, especially with emotional tension and/or the use of alcohol.
| 
