Being bullied has the same or worse long-term mental health outcomes as being maltreated by adults. Lee Morley/Flickr

Children who are bullied by their peers have worse long-term mental health consequences than those who have been abused by adults, a study has found.

A study published in The Lancet Psychiatry compared the mental health of young adults in the UK and US who had been maltreated by adults, bullied by other children or both during their childhood.

The team, which presented its findings at the Paediatric Academic Societies (PAS) annual meeting in San Diego, analysed data from over 4,000 UK patients looking at reports of maltreatment between the ages of eight weeks and 8.6 years, and bullying at the ages of eight, 10 and 13.

Mental health outcomes – including depression, anxiety, self-harm and suicide – was assessed at 18.

Researchers also looked at 1,273 US patients, with maltreatment and bullying data assessed at the ages of nine and 16, and mental health problems between 19 and 25.

Findings showed that in general, children were more likely to experience abuse from their peers than from their parents or other adults.

Results from the UK showed 8.5% were exposed to maltreatment by adults, 29.7% to bullying and 7% to both. In the US, 15% were maltreated, 16.3% were bullied and 9.8% were both.

After adjusting for factors like familial mental health problems, findings indicated that maltreatment alone did not increase the risk of mental health problems in the US group, but increased the risk of depression in the UK group.

Children who were bullied were most likely to suffer from mental health problems than those maltreated. Being both bullied and maltreated also increased the risk of overall mental health problems.

"Being bullied is not a harmless rite of passage or an inevitable part of growing up; it has serious long-term consequences," study author Dieter Wolke, said. "It is important for schools, health services and other agencies to work together to reduce bullying and the adverse effects related to it."