Some however, awake from a terrible dream, with their heart racing, and blood pressure high, but it may be near impossible for them to lie back down to sleep. This is especially true for children between the ages of about three to six (Aldrich 277). In a study of around 2000 children, 78% of the children had at least one parasomnia during the course of the study. A parasomnia as defined by Michael Aldrich, "Parasomnia are disorders in which undesirable physical and mental phenomena occur mainly or exclusively during sleep" (260). These can include, night terrors, sleepwalking, sleep drunkenness, sleep talking, and many others. These parasomnias are classified into four subgroups by the International Classification of Sleep Disorders: arousal, sleep-wake transition, rapid eye movement disorders, and a residual group. (268). .
The disorders that will be focused on are that of the arousal group including: night terrors, and sleepwalking. Night terrors (pavor nocturnes) are defined as " Episodes of agitation and apparent fear or terror arising abruptly from sleep during which the patient is only partially responsive and inconsolable" (Aldrich 262). These differ from nightmares because the victim will remember the next morning the episode if it was a nightmare, a night terror will leave the victim clueless in the morning. A child suffering from night terrors may awake screaming, with a rapid heartbeat, with eyes open yet they will not be conscious. In a nightmare, a child may wake screaming with a rapid heartbeat crying, but they will be alert and conscious. Night terrors will usually happen shortly after they fall asleep, as differing from nightmares that occur normally in the middle hours of sleep. Differing from night terrors, a nightmare is defined by Antonio Culebras as "intense dream anxiety attacks that frighten patients" (319). A nightmare is not a parasomnia, it happens to almost everyone at some point in time, most just shrug it off as another bad dream.