Night terror

A night terror, sleep terror or pavor nocturnus is a parasomnia or sleep disorder, causing feelings of terror or dread, and typically occurs during the first hours of stage 3-4 non-rapid eye movement (NREM) sleep. Night terrors tend to happen during periods of arousal from delta sleep, also known as slow-wave sleep. During the first half of a sleep cycle, delta sleep occurs most often, which indicates that people with more delta sleep activity are more prone to night terrors. However, they can also occur during daytime naps.

Night terrors have been known since the ancient times, although it was impossible to differentiate them from nightmares until rapid eye movement was discovered. While nightmares (bad dreams that cause feelings of horror or fear) are relatively common during childhood, night terrors occur less frequently according to the American Academy of Child and Adolescent Psychiatry. The prevalence of sleep terror episodes has been estimated at 1%-6% among children and at less than 1% of adults. Night terrors can often be mistaken for confusional arousal. Sleep terrors begin between ages 3 and 12 years and then usually dissipate during adolescence. In adults, they most commonly occur between the ages of 20 to 30. Though the frequency and severity vary between individuals, the episodes can occur in intervals of days or weeks, but can also occur over consecutive nights or multiple times in one night.

Night terrors are largely unknown to most people, creating the notion that any type of nocturnal attack or nightmare can be confused with and reported as a night terror.

Associated features
The universal feature of night terrors is inconsolability. During night terror bouts, patients are usually described as "bolting upright" with their eyes wide open and a look of fear and panic on their face. They will often scream. Furthermore, they will usually sweat, exhibit rapid respiration, 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 individual is trying to protect himself and/or escape from a possible threat which threatens bodily injury. Although children 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. Occasionally, when a person with a night terror is awakened, he will lash out at that person, which can be dangerous for that individual. Most people who experience this are amnesic, or partially amnesic from the incident the next day. Sleepwalking is another predisposition. Sleepwalking and night terrors are different manifestations of the same parasomnia.

During lab tests, subjects are known to have very high voltages of electroencephalography (EEG) delta activity, an increase in muscle tone, and a doubled increase in heart rate, if not more. Brain activities during a typical episode show theta and alpha activity when using an EEG. It is also common to see abrupt arousal from NREM sleep that does not progress into a full episode of a night terror. These episodes can include tachycardia. Night terrors are also associated with intense autonomic discharge of tachypnea, flushing, diaphoresis, and mydriasis.

In children with night terrors, there is no increased occurrence of psychiatric diagnoses. However, in adults who suffer from night terrors there is a close association with psychopathology or mental disorders. There may be an increased occurrence of night terrors - particularly among those suffering of having suffered from post-traumatic stress disorder (PTSD) and generalized anxiety disorder (GAD). It is also likely that some personality disorders may occur in individuals with night terrors, such as dependent, schizoid, and borderline personality disorders. There have been some symptoms of depression and anxiety that have increased in individuals that have suffered from frequent night terrors. Low blood sugar is associated with both pediatric and adult night terrors. A study of adults with thalamic lesions of the brain and brainstem have been occasionally associated with night terrors. Night terrors are closely linked to sleepwalking and frontal lobe epilepsy.

Susceptibility and variation
There is some evidence that a predisposition to night terrors and other parasomnias may be congenital. Individuals frequently report that past family members have had either episodes of sleep terrors or sleepwalking. In some studies, a ten-fold increase in the prevalence of night terrors in first-degree biological relatives has been observed—however, the exact link to inheritance is not known. Familial aggregation has been found suggesting that there is an autosomal mode of inheritance. In addition, some laboratory findings suggest that sleep deprivation and having a fever can increase the likelihood of a night terror episode occurring. Other contributing factors include nocturnal asthma, gastroesophageal reflux, and central nervous system medications. Special consideration must be used when the subject suffers from narcolepsy, as there may be a link. There have been no findings that show a cultural difference between manifestations of night terrors, though it is thought that the significance and cause of night terrors differ within cultures.

Also, older children and adults provide highly detailed and descriptive images associated with their sleep terrors than younger children, who either cannot recall or only vaguely remember. Sleep terrors in children are also more likely to occur in males than females; in adults, the ratio between sexes are equal. A longitudinal study examined twins, both monozygotic and dizygotic, and found that a significantly higher concordance rate of night terror was found in monozygotic twins than in dizygotic.

Though the symptoms of night terrors in adolescents and adults are similar, their etiologies, prognoses, and treatments are qualitatively different. There is some evidence that suggests that night terrors can occur if the sufferer does not eat a proper diet, does not get the appropriate amount or quality of sleep (e.g., because of sleep apnea), or is enduring stressful events. Adult night terrors are much less common and often respond best to treatments that rectify causes of poor quality or quantity of sleep.

DSM-IV-TR diagnosis
The DSM-IV-TR diagnostic criteria for sleep terror disorder requires:
 * recurrent periods where the individual abruptly wakes from sleeping with a scream
 * the individual experiences intense fear and symptoms of autonomic arousal such as increased heart rate, heavy breathing, and increased perspiration
 * the individual cannot be soothed or comforted during the episode
 * the individual is unable to remember details of the dream or details of the episode
 * the occurrence of the sleep terror episode causes clinically significant distress or impairment in the individual's functioning
 * the disturbance is not due to the effects of a substance or general medical condition

Adults
Night terrors in adults have been reported in all age ranges. Though the symptoms of night terrors in adolescents and adults are similar, the etiology, prognosis and treatment are qualitatively different. These night terrors can occur each night if the sufferer 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 adult night terrors and hypoglycemia.

When a night terror happens, it is typical for a person to wake up screaming 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 further investigate through an MRI procedure.

Children
Night terrors typically occur in children between the ages of three to twelve years, with a peak onset in children aged three and a half years old. An estimated one to six percent of children experience night terrors. Boys and girls of all backgrounds are affected equally. They usually resolves during adolescence. Sleep disruption is parents’ most frequent concern during the first years of a child’s life. Half of all children develop a disrupted sleep pattern serious enough to warrant assistance of a physician. In children younger than three and a half years old, peak frequency of night terrors is at least one episode per week. Among older children, peak frequency of night terrors is one or two episodes per month. Children experiencing night terrors may be helped by a paediatric evaluation. During such evaluation, the paediatrician may also be able to exclude other possible disorders that might cause night terrors.

Dream Content
There exists evidence suggesting the dream content of patients who suffer from sleepwalking or night terrors differs from those patients who suffer from REM sleep behavior disorder. In patients from both groups of disorders, the dream content varied based mainly on the fight or flight response: those suffering from sleepwalking or night terrors experienced dreams of fleeing a stressful stimulus while those suffering from REM sleep behavior disorder experience dreams in which they fight back against the stressful stimulus. The dreams of REM sleep behavior disorder patients are much more aggressive than the dreams of patients with sleepwalking or night terrors.

Treatment
In most children, night terrors eventually subside and do not need to be treated. It may be helpful to reassure the child that he or she will outgrow this disorder. Psychotherapy or counseling can be helpful in many cases. There is some evidence to suggest that night terrors can result from lack of sleep or poor sleeping habits. In these cases, it can be helpful to improve the amount and quality of sleep which the child is getting. If this is not enough, Benzodiazepine medications (such as diazepam) or tricyclic antidepressants may be prescribed to reduce the occurrence of night terrors; however, medication is only recommended in extreme cases.

Scheduled Awakenings
Scheduled awakening therapy is an option that has been shown to both prevent night terrors and cure night terrors in 9 out of 10 in children. Scheduled awakening therapy involves waking the child from sleep 15–30 minutes before the episodes typically occur to interrupt the sleep cycle and prevent the onset of a night terror. Despite the clinical success of scheduled awakenings, the therapy has not caught on as it is difficult to perform properly and consistently. It is not always clear when to time the intervention since the child may fall asleep at a different time night after night. Also, the child will be fully awake in the middle of the night which can have its own undesirable consequences.

In order to overcome some of the limitations with traditional scheduled awakening therapy, alternative treatment methods are being researched. One investigational treatment currently in research by the Caydian group at Stanford University involves the use of partial awakenings in place of full awakenings. Partial awakenings have the benefit of providing similar relief from night terrors without having to completely awaken the child. This avoids large disruptions in the child's sleep and avoids the child from becoming aware that such a therapy is even being performed.

Paroxetine
In an experiment performed by Nutt (1997) involving the use of paroxetine as a treatment for night terrors, a small population of patients with night terrors was given paroxetine to be taken in various doses for a period of time. In most cases, the night terrors were abolished, while those that were not abolished were at least reduced. Nutt concluded that paroxetine is a safe and effective treatment option that is comparable to benzodiazepine drugs in efficiency. However, patients do not build up a tolerance to paroxetine, which cannot be said of the benzodiazepine drugs. Since the experimental population size of the experiment was so small, more evidence should be gathered to further confirm Nutt's conclusions.