Sleep terrors differ from nightmares in that they occur during the later stages of non-REM sleep and are characterized by sudden screaming or yelling, panic, dilated pupils, increased heart rate, perspiring, and heavy or rapid breathing. The person experiencing the sleep terror seldom remembers anything about it. It is not uncommon for someone to hurt themselves or others who are trying to calm them down during an episode. If sleep terrors begin in childhood, the outlook is very good. Sleep terrors that begin in adulthood tend to be a chronic condition that comes and goes.
During a sleep terror, people often hit something or someone, get up out of bed in a panic, or even hurt themselves. It is always wise to take safety precautions to protect the sufferer and other family members.