LONDON — Babies who are breast-fed for several months develop fewer behavioural problems in early childhood than those who are bottle-fed, researchers have said.

The British study which involved around 10,000 mothers and their babies found that breastfeeding for at least four months lowered the risk of behavioural problems in children aged five by one third.

Researchers say the findings, published in the journal Archives of Disease in Childhood, add to a wealth of existing evidence on the benefits of breastfeeding.

Children raised on bottled milk formula tended to show more signs of anxiety, hyperactivity or lying and stealing, researchers found.

"We?re not necessarily talking about tearaway, unmanageable five-year-old kids," said Maria Quigley from Oxford University, who led the research.

"It might be unusual anxiousness, restlessness, inability to socialise with other children or play fully in groups."

Scientists said the results could be explained either by the fatty acids in breast milk which aid brain development or the bonding between mother and child, which may affect learned behaviour.

Researchers from the Universities of Oxford, Essex, York and University College London analysed data from a survey of 10,037 infants born in the UK between 2000 and 2001, who took part in the the wider Millennium Cohort Study.

Mothers were asked to assess the behaviour of their children by the age of five, giving scores for different behaviours, such as clinginess and restlessness.

Raw figures showed that only six percent of breast-fed children were given abnormal scores indicating behavioural problems, compared with 16 percent of formula-fed children.

However, mothers who breast-fed tend to be older, better educated and from a higher socio-economic background than those who don't, the study said.

Researchers therefore adjusted the figures to take those factors into account, concluding that there was a 30 percent greater risk of behavioural problems among formula-fed children.

"Our results provide even more evidence for the benefits of breastfeeding," Quigley added.

"Mothers who want to breastfeed should be given all the support they need."

Janet Fyle, from the Royal College of Midwives, agreed that the study backed evidence that breastfeeding is best for babies but warned against victimising women who choose not to.

"We need to be careful to keep a balance when interpreting the results, so that we do not send a negative message to mothers that they have failed or make them feel guilty because they bottle-fed their babies," she said.