Objective Studies have reported that breastfeeding promotes child cognitive ability. Others have suggested that any beneficial effects of breastfeeding are likely to be attributable to higher levels of education and socioeconomic status seen in breastfeeding mothers. We aimed to examine the effects of breastfeeding on cognitive development at one year, after adjusting for the main confounding variables including maternal education, socioeconomic status (SES), and infant stimulation in the home.

Method Mothers of 137 one-year-old infants were interviewed about sociodemographic factors and breastfeeding practices. Stimulation in the home was measured using the Home Observation for Measurement of the Environment (HOME) Inventory. Cognitive development was measured using the Mental Development Index (MDI) of the Bayley Scales of Infant Development.

Results Breastfeeding initiation rate was 70%. Mean (SD) duration of breastfeeding was 19 weeks (18.97). In initial linear regression analyses, variables not predictive of cognitive development were maternal age, marital status, smoking during pregnancy, education, SES, infant birth weight or infant birth order. Breastfeeding duration in weeks (β = 0.340, SE±0.044, p<0.0001), home environment (β = 0.228±SE 0.189, p = 0.007), and female gender (β = 0.209, SE±1.667, p = 0.014) predicted cognitive scores. In multiple regression, breastfeeding was the only significant predictor of cognitive scores, even after adjusting for confounding variables (standardised β = 0.285 SE±0.045, p = 0.001).

Conclusion Our data suggest that breastfeeding has a beneficial effect on cognitive development, and this is independent of major confounding variables, including stimulation in the home. Our study did not include a measure of maternal intelligence therefore these results should be interpreted with caution.