Frequent nightmares in childhood could indicate an increased risk of psychosis, according to research from the University of Warwick in the UK. The study authors have published their findings in the journal Sleep.

It is very common for young children to have nightmares. Having bad dreams is a normal part of growing up, and the frequency of nightmares usually decreases as the child grows older.

Nightmares happen during REM (rapid eye movement) sleep – one of the five stages that most people experience over the course of a night’s sleep. Adults spend, on average, about 90-120 minutes in REM sleep per night, with infants spending twice as much time in REM sleep.

While in REM sleep, the body’s muscles become paralyzed, but the brain goes into intense activity – working almost as hard as it does during wakefulness.

During REM sleep, people have very vivid dreams. After a bad dream, it is common to wake suddenly, full of fear and worry with a fast-beating heart.

Another sleep disorder experienced by young children is night terrors. These occur during “deep sleep,” usually in the first half of the night.

Night terrors are less common than nightmares and more physical. Children may scream or thrash about in their sleep, although they will typically have no memory of this when they wake up.

The new study looked at incidences of nightmares and night terrors in 6,700 children in the UK. The researchers assessed the children six times between the ages of 2 and 9 years, and then followed up with them at age 12 years.

The researchers found that the likelihood of experiencing psychotic experiences increased with the incidence of nightmares.

Children reporting one period of nightmares between the ages of 2 and 9 had a 16% increased risk of having a psychotic experience in adolescence. For children who reported three or more sustained periods of nightmares, the risk of psychotic experience jumped up by 56%.

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The researchers found that the likelihood of experiencing psychotic experiences increased with the incidence of nightmares.

When the children were interviewed at age 12, they were asked if they had experienced nightmares, night terrors, sleepwalking, delusions, hallucinations and thought interference in the past 6 months.

About a quarter of the 12 year olds reported having nightmares in the previous 6 months, with less than 1 in 10 experiencing night terrors in the same period.

Overall, children reporting frequent nightmares at the age of 12 were 3.5 times more likely to suffer psychotic experiences – such as hallucinations, interrupted thoughts or delusions – in early adolescence. Experiencing night terrors at the age of 12 doubled the risk of a psychotic experience.

Other sleep disorders, such as having problems with falling asleep or waking frequently during the night, did not seem to have any link with psychotic experiences.

Although the findings of this study seem alarming, the study authors urge readers to interpret the results with caution, as the data is based on the children’s own reports.

“We certainly don’t want to worry parents with this news,” says study author Prof. Dieter Wolke, “3 in every 4 children experience nightmares at this young age. However, nightmares over a prolonged period or bouts of night terrors that persist into adolescence can be an early indicator of something more significant in later life.”

Lucie Russell, director of campaigns at the children and young people’s mental health charity YoungMinds, says:

This is a very important study because anything that we can do to promote early identification of signs of mental illness is vital to help the thousands of children that suffer. Early intervention is crucial to help avoid children suffering entrenched mental illness when they reach adulthood.”