The Association Between Duration of Breastfeeding and Adult Intelligence

The objective of this study was to determine the association between duration of infant breastfeeding and intelligence in young adulthood. This prospective longitudinal birth cohort study was conducted in a sample of 973 men and women and a sample of 2280 men, all of whom were born in Copenhagen, Denmark, between October 1959 and December 1961. The samples were divided into 5 categories based on duration of breastfeeding, as assessed by physician interview with mothers at a 1-year examination. Independent of a wide range of possible confounding factors, a significant positive association between duration of breastfeeding and intelligence was observed in these 2 independent samples of young adults, assessed with 2 different intelligence tests.