The association remained even after controlling for a wide range of maternal and socioeconomic factors.
Other findings from the MCS, the 1958 National Child Development Study and the 1946 British birth cohort have found associations between breastfeeding and children’s scores on various assessments of general ability as early as 3 years and as old as 15.
Another study of the 1946 British birth cohort concluded that the benefits of breastfeeding on cognition can last well into adult life. Researchers found that people who were breastfed for longer as infants had slightly better reading ability at age 53. This was largely due to the connection between breastfeeding and improved cognitive ability at age 15.
However, other research has suggested that better cognitive function is only associated with, and not caused by, breastfeeding.
A study of the children of the 1946 cohort members found that the association between breastfeeding and cognitive development was explained by either father’s social class, mothers’ education, or mother’s cognitive function.
Another study of 5,475 children taking part in the US National Longitudinal Survey of Youth 1979 found no effect of breastfeeding on the children’s cognitive function, once their mother’s IQ had been taken into account. The association between breastfeeding and cognitive development was significantly reduced when controlling for mother’s IQ, and became statistically insignificant when controlling for other related factors, such as mother’s education, mother’s age at birth, and family socioeconomic circumstances.
