Breastfeeding's calming effects seem to be long-lasting.

Years after being weaned, breastfed children cope better with stressful situations like their parents' divorce than their bottle-fed peers, researchers said on Thursday.

"In children who are breast-fed, there is less of an association between parental divorce and separation and childhood anxiety," Dr Scott Montgomery, an epidemiologist at the Karolinska Institute in Sweden, said in an interview.

Breast milk is full of nutrients, hormones, enzymes, growth factors and antibodies that are passed from mother to child.

Research has shown breast-feeding reduces infections, respiratory illness and diarrhea in the child and cuts the risk of post-birth bleeding in the mother.

In an observation study published in the journal Archives of Disease in Childhood, Montgomery and his team studied how breast- and bottle-fed 10-year-olds coped with the stress of their parents' marital problems.

The children were among 9,000 youngsters who had been monitored from birth for a major British study. Their teachers were asked to rate their anxiety level on a scale of 0 to 50.

There was a higher level of stress in all the children but the breastfed youngsters coped better.

"The anxiety was much less obvious in children who were breastfed," Montgomery said.

The researchers do not know why breastfed babies were less anxious. They suggested breastfeeding could be an indicator of other parental factors or the physical contact between the mother and the child may have helped to reduce anxiety.

Breastfeeding could also influence the development of pathways in the body linked with its response to stress.

"The more we look at breastfeeding, the more benefits we see. As this is something that is, in evolutionary terms, normal it is likely to be important in normal human development," Montgomery said.