Nightmares are dreams with vivid and disturbing content. They are most common in children during REM sleep, but they can happen to adults as well. They usually involve and immediate awakening and good recall of the dream. Sleep terrors, also common in children, are often described as extreme nightmares that take place during non-REM sleep.
Sleep terrors have common characteristics. They usually include arousal, agitation, large pupils, sweating, and increase blood pressure. Usually the child screams and appears terrified for several minutes until they eventually relax and return to sleep. Sleep terrors usually take place early in the night and may be combined with sleepwalking. The child typically does not remember or only has a vague memory of their dream.