Twelve-year-old children are much more likely to suffer from nightmares, night terrors or sleep walking if they were bullied between the ages of eight and 10, a new study has found.

Sleep-related disorders such as nightmares and night terrors are known as parasomnias. UK researchers decided to look into these in relation to bullying.

They interviewed children aged between eight and 10 about their experiences of bullying. The children were then interviewed about parasomnias when they were aged 12 and 13.

"We found children who were bullied at age eight or 10 years were more likely to have nightmares, night terrors or sleepwalking at age 12 years. Moreover, those who were bullied and bullied others were most likely to have any parasomnia," commented Prof Dieter Wolke of the University of Warwick.

He noted that as with previous studies, ‘being a female, having persistent sleep problems, and emotional and behaviour problems in childhood additionally increased the risk for parasomnias at age 12 years'.

The researchers believe that stress has a key role to play in the link between bullying and parasomnias.

"Nightmares may occur when anxiety exceeds a threshold level and several studies have suggested that trait anxiety may be related to the frequency of parasomnias. However, even after controlling for pre-existing anxiety problems, our results showed that being bullied may increase the risk for parasomnias," said Dr Suzet Tanya Lereya, also of the University of Warwick.

The researchers suggested that if a child often experiences parasomnias, parents, teachers and healthcare providers should consider asking them if they are being bullied.

"This would allow detecting bullied children and providing the help they need at an early time to reduce the negative effects of being bullied," they added.

Details of these findings are published in the journal, Pediatrics.