Only 6 percent of the breastfed children showed signs of behavior problems compared with 16 percent of the formula-fed children, even when controlling for age, education, and socio-economic background of the mother.
Researchers propose the effect may be due to the make-up of the breastmilk, which containes large amounts of a particular type of fatty acid, as well as growth facotrs and hormones which aid in brain and nervous system development
As an alternative theory, researchers also say that breastfeeding may lead to better mother-baby interaction.
Breastfeeding has previously been linked with other health benefits for babies, including lower rates of infection and less obesity in later life.
The study was published in the journal Archives of Disease in Childhood.
