Search

Breastfeeding has been consistently associated with higher intelligence since childhood. However, this relation could be confounded due to maternal selection bias. We estimated the association between predominant breastfeeding and intelligence in school‐age children considering potential selection bias and we simulated the intelligence gap reduction between low versus higher socioeconomic status children by increasing breastfeeding. We analysed predominant breastfeeding practices (breastmilk and water‐based liquids) of children 0–3 years included in the Mexican Family Life Survey (MxFLS‐1). Intelligence was estimated as the z‐score of the abbreviated Raven score, measured at 6–12 years in the MxFLS‐2 or MxFLS‐3. We predicted breastfeeding duration among children with censored data with a Poisson model. We used the Heckman selection model to assess the association between breastfeeding and intelligence, correcting for selection bias and stratified by socioeconomic status. Results show after controlling for selection bias, a 1‐month increase in predominant breastfeeding duration was associated with a 0.02 SD increase in the Raven z‐score (p < 0.05). The children who were predominantly breastfed for 4–6 months versus <1 month had 0.16 SD higher Raven z‐score (p < 0.05). No associations were found using multiple linear regression models. Among low socioeconomic status children, increasing predominantly breastfeeding duration to 6 months would increase their mean Raven z‐score from −0.14 to −0.07 SD and reduce by 12.5% the intelligence gap with high socioeconomic status children. In conclusion, predominant breastfeeding duration was significantly associated with childhood intelligence after controlling for maternal selection bias. Increased breastfeeding duration may reduce poverty‐driven intelligence inequities. Key messages: An increase in predominant breastfeeding duration was positively and significantly associated with intelligence in school‐aged children.The most significant increase in intelligence was found among those who were predominantly breastfed for 4–6 months compared with less than 1 month.The association was stronger among children with low socioeconomic status. Hence, increased breastfeeding duration may reduce the intelligence gap between low versus high socioeconomic‐status children.Selection bias between breastfed and nonbreastfed children should be considered in future analyses in this area. [ABSTRACT FROM AUTHOR]