Bottle-fed tots bigger, happier ... and calmer
Bottle-fed babies tend to be quieter and apparently more content because they are "comfort eating", according to a new research.
By contrast, breastfed babies cry more, laugh less and generally have "more challenging temperaments" than formula-fed infants, the study has found.
But such behaviour is normal, and mothers should learn to cope with it rather than reach for the bottle, according to researchers.
Infant irritability was said to be a natural part of the "dynamic communication" between mothers and babies.
The study rated the temperament of 316 babies at age three months using a 191-item behaviour questionnaire completed by their mothers.
Scores differed between babies that were exclusively breast-fed, bottle-fed or mixed-fed.
In three broad areas, breast and mixed-fed babies were rated as being more difficult to deal with than bottle-fed babies.
The study authors wrote in the online journal Public Library of Science ONE: "In particular, compared to formula-fed infants, breastfed infants were reported to show greater distress, less smiling, laughing and vocalisation, to be slower to calm down following distress or excitement, and more difficult to soothe by care givers."
The findings may help explain why so many mothers give up on breastfeeding after a short time, despite the strong health message that "breast is best" for growing infants. Health guidelines say mothers should exclusively breastfeed their babies for the first six months after birth.
Study leader Dr Ken Ong, urged mothers to persevere despite the difficulties -- and seek help if they need it.
"There is an overwhelming body of evidence supporting breastfeeding as the normal and most healthy form of infant nutrition, and our findings do not contradict this," he said.
"Bottle-fed babies may appear more content, but research suggests that these infants may be over-nourished and gain weight too quickly. Our findings are essentially similar to other stages of life; people often find that eating is comforting."