The prevalence of sleep terrors in general is unknown. The number of small children who experience sleep terror episodes (distinct from sleep terror disorder, which is recurrent and causes distress or impairment) are estimated at 36.9% at 18 months of age and at 19.7% at 30 months. In adults, the prevalence is lower, at only 2.2%. Night terrors have been known since ancient times, although it was impossible to differentiate them from nightmares until rapid eye movement was studied. Signs and symptoms
The universal feature of night terrors is inconsolability, very similar to that of a panic attack. During night terror bouts, people are usually described as "bolting upright" with their eyes wide open and a look of fear and panic on their faces. They will often yell, scream, or attempt to speak, though such speech is often incomprehensible. Furthermore, they will usually sweat, exhibit rapid breathing, and have a rapid heart rate (autonomic signs). In some cases, individuals are likely to have even more elaborate motor activity, such as a thrashing of limbs—which may include punching, swinging, or fleeing motions. There is a sense that the individuals are trying to protect themselves and/or escape from a possible threat of bodily injury. Although people may seem to be awake during a night terror, they will appear confused, be inconsolable and/or unresponsive to attempts to communicate with them, and may not recognize others familiar to them.
Though the symptoms of night terrors in adolescents and adults are similar, the cause, prognosis and treatment are qualitatively different. These night terrors can occur each night if the individual does not eat a proper diet, get the appropriate amount or quality of sleep (e.g. sleep apnea), is enduring stressful events, or if he or she remains untreated. Adult night terrors are much less common, and often respond to treatments to rectify causes of poor quality or quantity of sleep. Night terrors are classified as a mental and behavioral disorder in the ICD. A study done about night terrors in adults showed that other psychiatric symptoms were prevalent in most patients experiencing night terrors hinting at the comorbidity of the two. There is some evidence of a link between night terrors and hypoglycemia.When a night terror happens, it is typical for a person to wake up yelling and kicking and to be able to recognize what he or she is saying. The person may even run out of the house (more common among adults) which can then lead to violent actions. It has been found that some adults who have been on a long-term intrathecal clonidine therapy show side effects of night terrors, such as feelings of terror early in the sleep cycle. This is due to the possible alteration of cervical/brain clonidine concentration. In adults, night terrors can be symptomatic of neurological disease and can be further investigated through an MRI procedure.