Hold the guilt! Yet more evidence that breastfeeding has NO impact on cognitive development.


A new study shows — yet again — that breastfeeding has NO benefit for cognitive development.

Let’s start with the money quote from Associations between breastfeeding and cognitive function in children from early childhood to school age: a prospective birth cohort study published yesterday in the International Breastfeeding Journal:

Any observed benefit of breastfeeding on cognitive development DISAPPEARS when corrected for maternal IQ.

Breastfeeding should not be interpreted to have medical benefits for cognitive development.

The key point in the study is that any observed benefit of breastfeeding on cognitive development DISAPPEARS when corrected for maternal IQ.

The authors started with the following premise:

Despite evidences of breastfeeding for preventing acute physical illnesses in infants, the evidence for the association between breastfeeding and long-term cognitive development is not yet convincing.

How did they test the premise?

The data of nationwide representative sample of 1752 children born between 2008 and 2009 in Korea were prospectively assessed from the fetal period to examine the benefits of breastfeeding and cognitive development. Breastfeeding duration was prospectively assessed by parents. The Korean Ages and Stages Questionnaire and the Korean version of Denver II were used to assess early development annually from 5.5 to 26.2 months of age. Language development at 3 years of age was assessed with Receptive and Expressive Vocabulary Tests. Cognitive function at 8 years of age was assessed using multifactorial intelligence test.

What did they find?

The following chart shows the comparison of cognitive scores on a variety of tests at various ages based on the duration of breastfeeding. Statistically significant differences appear in bolded type. (Full size chart here.)


At the far right of the chart is the crude comparison between children who were ever breastfed and children who were never breastfed. Only 2 of the 9 cognitive tests showed statistically significant differences. The rest showed no difference.

But even those few statistically significant differences DISAPPEARED when adjusted for children’s sex, age, gestational age, birth weight, parental educational level, and household income level (circled results).

In other words, any observed differences in IQ were the result of factors OTHER than breastfeeding.

The authors conclude:

… Many previous studies support the finding that there are positive associations between breastfeeding and cognitive development. However, the mean difference (effect size) in cognitive development due to breastfeeding was only 3.44 points (about one-third of a standard deviation), which is reduced again by the adjustment for maternal IQ. Considering these findings comprehensively, breastfeeding is not considered a critical factor in the cognitive development of children. Other studies have also reported that the observed advantage of breastfeeding on IQ score is actually due to genetic and socioenvironmental factors. When the results are adjusted for covariates such as maternal IQ, the effect of breastfeeding on cognitive function was insignificant. Thus, breastfeeding should not be interpreted to have medical benefits for cognitive development…

This should not be news to anyone who has followed breastfeeding research in for the past decade.

In 2014 the study, Is Breast Truly Best? Estimating the Effects of Breastfeeding on Long-term Child Health and Wellbeing in the United States Using Sibling Comparisons was published by Colen and Ramey.

The authors looked at the impact of breastfeeding on 11 different variables (including several measurements of cognitive development) in three different groups. There were difference between breastfed and bottle fed children in 10 of the 11 measured variables when looking at children overall. Those differences persisted when comparing families in which all the children were breastfed to families where all the children were bottlefed. But when the authors looked within families, there was no significant difference between breastfed and bottle fed children.

Looking within families takes ethnic, cultural and socio-economic factors out of the picture. When you do that, you find NO difference (including NO cognitive difference) between breastfed and bottlefed children.

In other words breastfeeding is a proxy for other factors that impact cognitive development. Since women who breastfeed are more likely to have higher IQ, higher educational achievement and higher socio-economic status, their children end up with higher IQ. It’s NOT the breastfeeding that causes the increased IQ, it’s the maternal advantages that lead to the resulting enhanced cognitive development.

What does this mean?

While every mother should be able to breastfeed for as long she wants to do so, there is NO reason to feel guilty if you don’t want to breastfeed or don’t want to breastfeed for long.

Hold the guilt! The benefit of breastfeeding on cognitive development has been overstated. It is time to correct our advice to mothers to reflect the real benefits of breastfeeding, not imagined benefits that don’t exist.