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15-01-2012 | Psychology | Article

Breastfed babies ‘more irritable’ than formula milk-fed babies


Free abstract

MedWire News: Breastfed babies are more likely to show distress, and less likely to smile, laugh, and vocalize, or be able to be soothed than are formula-fed babies, UK researchers say.

However, rather than being a sign of stress, this greater irritability is a part of the "dynamic communication" between mothers and babies and should not deter women from breastfeeding, said lead author Ken Ong (Medical Research Council Epidemiology Unit, Cambridge) in a press statement.

Ong and team's analysis included 316 infants born between January 2006 and February 2009 for whom information on infant and milk-feeding at the age of 3 months was available. Infant temperament at the age of 3 months was reported by the mother using the Revised Infant Behavior Questionnaire, which provides an assessment of three major dimensions of infant temperament.

These temperaments are: surgency/extraversion, where a higher score indicates high activity levels, impulsivity, and positive affect in response to highly stimulating situations; negative affectivity, where a higher score is seen in more distressed infants; and orienting/regulation, where a higher score is associated with good ability to regulate own emotions.

Overall, 137 infants were exclusively breastfed, 88 were exclusively formula-fed, and 91 were fed with a mixture of formula and breastfeeding at the age of 3 months.

Exclusively breastfed and mixed-fed infants were rated as having significantly lower impulsivity and positive responses to stimulation than formula milk-fed babies, at adjusted mean surgency/extraversion scores of 4.0 each versus 4.3, respectively.

Breastfed babies also had a significantly lower ability to regulate their own emotions, with a mean orienting/regulation score of 4.9, than did formula milk-fed babies, who had a mean score of 5.1.

Breastfed babies also had significantly higher emotional instability than formula-fed babies, with mean negative affectivity scores of 3.0 versus 2.8, respectively.

The authors suggest that the increased perceived "irritable" behaviors seen in breastfed babies could be due to the fact that although humans often believe infant crying to be a sign of stress, for infant animals it is a "normal component of signaling to parents."

They continue: "The expression of offspring demand is part of a dynamic signaling system between parents and offspring."

They add that crying and irritability could act as a sign of nutritional need during early infancy rather than later infancy and explain that this could underlie the "less challenging" temperament that has been observed in breastfed babies at 6-12 months.

"These findings should not be taken to discourage mothers to breastfeed, but rather may suggest new potential avenues to improve breast-feeding duration."

Ong et al conclude in the journal PLoS One: "Increased awareness of the behavioral dynamics of breastfeeding, a better expectation of normal infant temperament and support to cope with difficult infant temperament could potentially help to promote successful breastfeeding."

By Piriya Mahendra

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