title: Breastfeeding and intelligence: a systematic review and meta-analysis.
abstract: OBJECTIVE
  This study was aimed at systematically reviewing evidence of the association between breastfeeding and performance in intelligence tests.
  
  
  METHODS
  Two independent searches were carried out using Medline, LILACS, SCIELO and Web of Science. Studies restricted to infants and those where estimates were not adjusted for stimulation or interaction at home were excluded. Fixed- and random-effects models were used to pool the effect estimates, and a random-effects regression was used to assess potential sources of heterogeneity.
  
  
  RESULTS
  We included 17 studies with 18 estimates of the relationship between breastfeeding and performance in intelligence tests. In a random-effects model, breastfed subjects achieved a higher IQ [mean difference: 3.44 points (95% confidence interval: 2.30; 4.58)]. We found no evidence of publication bias. Studies that controlled for maternal IQ showed a smaller benefit from breastfeeding [mean difference 2.62 points (95% confidence interval: 1.25; 3.98)]. In the meta-regression, none of the study characteristics explained the heterogeneity among the studies.
  
  
  CONCLUSIONS
  Breastfeeding is related to improved performance in intelligence tests. A positive effect of breastfeeding on cognition was also observed in a randomised trial. This suggests that the association is causal.
authors.affiliation: Postgraduate Program in Epidemiology, Universidade Federal de Pelotas, Pelotas, Brazil.
authors.forename: Bernardo L
authors.initials: BL
authors.lastname: Horta
authors.affiliation: Postgraduate Program in Epidemiology, Universidade Federal de Pelotas, Pelotas, Brazil.
authors.forename: Christian
authors.initials: C
authors.lastname: Loret de Mola
authors.affiliation: Postgraduate Program in Epidemiology, Universidade Federal de Pelotas, Pelotas, Brazil.
authors.forename: Cesar G
authors.initials: CG
authors.lastname: Victora
mesh_terms: D000293:Adolescent; D001942:Breast Feeding; D002648:Child; D002675:Child, Preschool; D003071:Cognition; D005260:Female; D006801:Humans; D007223:Infant; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D016032:Randomized Controlled Trials as Topic; D002094:Republic of Belarus; D006113:United Kingdom
keywords: Breastfeeding; Intelligence test; Meta-analysis; Systematic review