Bully victims are more likely to suffer from sleep walking, night terrors or nightmares by the time they are 12 years old, according to a recent study.

Researchers from the University of Warwick in the United Kingdom have found that being bullied increases the risk for a category of sleep disorders known as parasomnias. These are sleep-related problems such as nightmares, night terrors or sleep walking.

"We found children who were bullied at age 8 or 10 years were more likely to have nightmares, night terrors, or sleepwalking at age 12," researcher Dieter Wolke said in a statement. "Moreover, those who were bullied and bullied others were most likely to have parasomnia."

For the study, Wolke and his team interviewer a cohort of children between the ages of 8 and 10 years about bullying experiences and then about parasomnias when they were 12 to 13 years old.

"Consistent with previous studies, being a female, having persistent sleep problems, and emotional and behavior problems in childhood additionally increased the risk for parasomnias at age 12 years," Wolke said.

Researcher Suzet Tanya Lereya added that stress could be an important mechanism for the association between being bullied and parasomnias.

Nightmares may sometimes occur when anxiety exceeds a threshold level, several studies have suggested that anxiety may be related to the frequency of parasomnias, she added. However, even after controlling for pre-existing anxiety problems researchers found that being bullied may increase the risk for parasomnias.

"If a child is experiencing frequent parasomnias, parents, teachers, school counselors, and clinicians may consider asking about bullying. This would allow detecting bullied children and providing the help they need at an early time to reduce the negative effects of being bullied," researchers suggested.

The findings were recently published in Pediatrics, the journal of the American Pediatric Association.