Some benefits of breastfeeding are already well known -- for example breastfed babies have lower rates of infections, and mothers who breastfeed have a reduced risk of breast cancer.

In a study in the Archives of Disease in Childhood journal, British researchers used a "strengths and difficulties" questionnaire completed by parents about their children and found that abnormal scores were less common in children who were breastfed for at least four months.

Maria Quigley of the national perinatal epidemiology unit at Oxford University, who led the work, said the findings "provide even more evidence for the benefits of breastfeeding."

"Mothers who want to breastfeed should be given all the support they need. Many women struggle to breastfeed for as long as they might otherwise like, and many don't receive the support that might make a difference," she said in a statement.

They used data on whether mothers had breastfed and how long for and combined these with the results of the "strengths and difficulties" questionnaire used for identifying children with possible behavioral problems.

They found abnormal scores for the questionnaires, which indicate potential behavioral problems, were less common in children breastfed for at least four months -- at 6 percent --than in formula fed children -- at 16 percent.

The lower risk of a full-term breastfed child having abnormal scores for behavior was also evident even when the researchers took into account other important influences such as socio-economic or parental factors.