There is a lot of talk in the news lately about a new study published by the U.K.’s University of Warwick in the journal Sleep, which points to an as-yet-unexplained connection between sleep terrors and nightmares, if in high enough frequency in childhood, and future problems with psychosis. But little is said about the difference between the nightmares we all know, and sleep terrors.
The U.K. study worked with 6,800 children aged two to nine, analyzing the subjects six or more times to gather data about the children’s sleep patterns, frequency of nightmares and night terrors, and then revisited the subject again with the families when the children reached 12 years. All of the children experienced nightmares at one point in the study, but 37 percent of them experienced long periods of nightmare activity that lasted up to several years.
The researchers found significant correlation between the frequency and amount of sleep terrors and nightmares suffered by the youngsters and incidence of delusions and hallucinations in later years. Children who had only one period in their lives where they had persistent and long-term nightmares had approximately 16 percent chance of having some kind of psychotic experience later in life. Children who experienced three or more such periods of persistent nightmares were shown to have up to a 56 percent higher risk of developing psychotic symptoms.
The researchers went out of their way to state that not all children who experience a period of frequent nightmares would develop psychoses, saying only that there seems to be a relationship between the two mental events. Whether anything in the relationship is causal or dependably predictive is as yet unknown. In fact, there is already established evidence that 47 in 1,000 children may experience a psychotic event in their lives, and there is no way to know how many of these children have had similar intense nightmare periods. After all, most children experience heavy nightmare activity at some point in their first ten years.
Nightmares were not the only factor, however. Children in the study who had night terrors (also called sleep terrors) were found to have almost double the risk of developing future psychoses.
What are sleep terrors, as opposed to nightmares, and what are the differences between them? According to Sharon O’Brien of Presbyterian Sleep Health in Charlotte, NC, while nightmares occur during REM sleep as a function of fears invading the dream cycle, sleep terrors are somewhat harder to explain. For one thing, these events occur not during a dream cycle–not during REM sleep at all–but during slow-wave sleep. This is the kind of deep and normally restful sleep humans usually experience at the beginning of the sleep cycle before REM sleep begins.
Sleep terrors occur most often in children between the ages of three and 12. Rather than the normal restful slow-wave sleep, they have rather startling symptoms, including fast heartbeats, sweating, irregular breathing, and dilated pupils. Children with sleep terrors have been known to run through the house crying or screaming, and often their eyes are wide open during the event, though they appear to retain no memory of the occurrence after the fact.
Statistically boys are more often afflicted with sleep terrors than are girls; at least when the events take place in childhood. Adult sleep terrors are rare, though if they do occur in adulthood they seem to be equally distributed between the sexes.
Diagnosis of the symptoms is even more muddied by the fact that there are also a class of sleep-related events called nocturnal seizures, which can present almost exactly like sleep terrors, and involve children and adults walking around persistently unaware of any dangers around them, eyes open and agitated, and waking with no memory of the occurrence.
Because of the similarity, sleep terrors, like nocturnal seizures, can be classified as coming from higher than normal activity levels and possibly electrical activity taking place in the brain. One of the few differences between the two is that sleep terrors usually last longer than nocturnal seizures, which can be relatively short in duration.
Because sleep terrors can be considered to be a function of abnormally high levels of activity in the sleeping brain at a time when the brain usually rests in slow-wave sleep, further research must be done to discover the nature of the link between sleep terrors and possible later psychoses. For now, sleep terrors and nightmares, though surely different, are both a normal part of childhood and a possible harbinger of worse difficulties.
By Kat Turner
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