British researchers say people who are bullied as children have twice the risk of having delusions, hallucinations or other psychotic symptoms as pre-teens as those who have not been bullied.

They said bullying - especially when it is severe or chronic - can have serious consequences for some children, and may even act as a trigger for people who are genetically predisposed to schizophrenia.

"Chronic or severe peer victimisation has non-trivial, adverse, long-term consequences," Andrea Schreier of the University of Warwick in Coventry, England, and colleagues wrote in the Archives of General Psychiatry.

Several studies have shown that traumatic events in childhood such as physical or sexual abuse are linked with the development of psychosis in adulthood.

People who display psychotic symptoms in childhood are also more prone to develop schizophrenia as adults.

Dr Schreier and colleagues wanted to see if bullying might bring about some of these symptoms in adolescents.