Children frequently bullied by their siblings are twice as likely to have depression as young adults, a British study says.

LONDON, PAA - Children who are frequently bullied by their brothers or sisters are more likely to be depressed and even harm themselves in early adulthood, experts say.

Researchers say being the victim of bullying by peers is associated with an increased risk of psychological problems and wanted to assess whether the same impact was noted if a person's sibling or siblings were the perpetrators.

They examined data from youngsters from the UK, who said they were the victims of sibling bullying when they were aged 12 and assessed them when they were 18.

According to the researchers from the Universities of Oxford, Warwick and Bristol and University College London, children bullied by siblings were also twice as likely to say they had self-harmed within the previous year compared with those who had not been bullied.

If the figures were extrapolated, sibling bullying could account for 13 per cent of depression and 19 per cent of self harm among 18-year-olds, the authors said.

Lead author Dr Lucy Bowes, of the University of Oxford, said: "Forms of bullying where victims are shoved around the playground or targeted at work have been well documented. However, this study uncovers a largely hidden form of bullying.

"Victims of sibling bullying are offered little escape as sibling relationships endure throughout development.

"We are not talking about the sort of teasing that often goes on within families, but incidents that occur several times a week, in which victims are ignored by their brothers or sisters, or are subjected to verbal or physical violence."

The study, published in the journal Pediatrics, examined data on almost 3500 children who provided information on bullying and psychiatric issues. Of the children, 1810 said they had not been bullied by a brother or sister and 786 said they had been bullied several times a week.

Of those who had never been bullied by a sibling, 6.4 per cent had depression at age 18, 9.3 per cent experienced anxiety and 7.6 per cent had self-harmed in the previous year.

Meanwhile, depression was present in 12.3 per cent of those who said they had been bullied by a brother or sister several times a week when they were age 12, 14.1 per cent had harmed themselves in the previous year and 16 per cent reported anxiety.

"Social learning and how to behave with peers starts at home, and when siblings are bullied it can have serious long-term consequences, as we found in our study," said co-author Professor Dieter Wolke, of the University of Warwick.

"It is important that parents set clear rules about what is allowed in conflicts and they should intervene consistently when their children maltreat each other repeatedly."

Emma Jane Cross, the chief executive of charity BeatBullying said: "Being bullied as a child can have a devastating effect which lasts a lifetime.

"Parents who are concerned about this issue should speak to their children as early as possible before the problem escalates. It's important to tackle the underlying issues behind more frequent bullying behaviour rather than dismissing it as normal sibling rivalry."

Copyright AAP 2014