title: Breastfeeding, Cognitive and Noncognitive Development in Early Childhood: A Population Study.
abstract: OBJECTIVE
  There is mixed evidence from correlational studies that breastfeeding impacts children's development. Propensity score matching with large samples can be an effective tool to remove potential bias from observed confounders in correlational studies. The aim of this study was to investigate the impact of breastfeeding on children's cognitive and noncognitive development at 3 and 5 years of age.
  
  
  METHODS
  Participants included ∼8000 families from the Growing Up in Ireland longitudinal infant cohort, who were identified from the Child Benefit Register and randomly selected to participate. Parent and teacher reports and standardized assessments were used to collect information on children's problem behaviors, expressive vocabulary, and cognitive abilities at age 3 and 5 years. Breastfeeding information was collected via maternal report. Propensity score matching was used to compare the average treatment effects on those who were breastfed.
  
  
  RESULTS
  Before matching, breastfeeding was associated with better development on almost every outcome. After matching and adjustment for multiple testing, only 1 of the 13 outcomes remained statistically significant: children's hyperactivity (difference score, -0.84; 95% confidence interval, -1.33 to -0.35) at age 3 years for children who were breastfed for at least 6 months. No statistically significant differences were observed postmatching on any outcome at age 5 years.
  
  
  CONCLUSIONS
  Although 1 positive benefit of breastfeeding was found by using propensity score matching, the effect size was modest in practical terms. No support was found for statistically significant gains at age 5 years, suggesting that the earlier observed benefit from breastfeeding may not be maintained once children enter school.
authors.affiliation: School of Public Health, Physiotherapy, and Sports Science, lisa.girard@ucd.ie.|Geary Institute for Public Policy, and.
authors.forename: Lisa-Christine
authors.initials: LC
authors.lastname: Girard
authors.affiliation: Geary Institute for Public Policy, and.|UCD School of Economics, University College Dublin, Dublin, Ireland; and.
authors.forename: Orla
authors.initials: O
authors.lastname: Doyle
authors.affiliation: School of Public Health, Physiotherapy, and Sports Science.|Geary Institute for Public Policy, and.|Research Unit on Children's Psychosocial Maladjustment (GRIP).|Departments of Pediatrics, and.|Psychology, Université de Montreal, Montreal, Canada.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Tremblay
mesh_terms: D001942:Breast Feeding; D002657:Child Development; D002675:Child, Preschool; D003071:Cognition; D005260:Female; D006801:Humans; D007223:Infant; D007494:Ireland; D008137:Longitudinal Studies; D008297:Male; D057216:Propensity Score; D012042:Registries