Breastfeeding and verbal ability of 3-year-olds in a multicity sample

Our goal was to analyze the effect of maternal verbal ability and education on the association between breastfeeding and children's cognitive functioning. First, we hypothesized that maternal verbal abilities account for a large portion of the association between breastfeeding and child verbal abilities. Second, we hypothesized that after adjusting for maternal verbal abilities, a positive effect of breastfeeding will be most evident among highly educated mothers, because these mothers may have more opportunity to engage in cognitively stimulating parenting than do mothers with less education.

With data on 1645 American-born mothers participating in a longitudinal birth cohort study, we used linear regression to determine the influence of breastfeeding for at least 1 month on the Peabody Picture Vocabulary Test-Third Edition scores of 3-year-old children. Models were adjusted for an extensive set of demographic characteristics, including mother's Peabody Picture Vocabulary Test and the Home Observation for Measurement of the Environment score. Mothers were categorized into 1 of 3 educational-status groups: no high school diploma, high school diploma, and some post-secondary education.

In unadjusted mean comparisons, breastfed children had Peabody Picture Vocabulary Test scores that were 6.6 points higher than children who were not breastfed. After adjusting for demographic characteristics and maternal verbal ability, the coefficient dropped to 1.72. Among mothers with education beyond high school, the children's Peabody Picture Vocabulary Test scores in adjusted models were 2.2 points higher for breastfed children. Among mothers with a high school diploma or less, there were no significant differences in the children's Peabody Picture Vocabulary Test scores by breastfeeding status. These results were consistent in white, black, and Hispanic children.

Maternal Peabody Picture Vocabulary Test scores mediate much of the association between breastfeeding and child verbal abilities. The beneficial effects of breastfeeding on children's cognition may emerge only when breastfeeding is done in conjunction with other positive parenting behaviors. The advantageous effects of breastfeeding do not seem to be solely attributable to the superior nutrient content of breast milk.