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.

7 Responses to “Hold the guilt! Yet more evidence that breastfeeding has NO impact on cognitive development.”

  1. demodocus
    November 4, 2020 at 6:16 pm #

    Can’t prove it yet, but I suspect my younger child will do better in academics than my elder child; being breastfed didn’t prevent his likely case of ADHD. YC was eff, but she’s already enjoying practicing her letters more than her brother ever has. (They are about equivalent in intelligence, just different focuses. When the 1st grader focuses in the first place.)

  2. carovee
    October 9, 2020 at 11:46 am #

    I beat myself up so much because I couldn’t produce enough milk. I sat up pumping at night when I should have been sleeping. I forced my son to try and try and try to latch on to my soft nipples. 11 years later I look back and wonder what the heck was I thinking. It was so much unnecessary pain and anxiety. Please, just feed your babies in whatever way works best for you and be happy.

    • PeggySue
      October 9, 2020 at 7:40 pm #

      It sounds like you went through a lot. I’m so sorry.

  3. fiftyfifty1
    October 1, 2020 at 2:51 pm #

    Thank you for reporting on this study. Purported cognitive benefit was the reason I breastfed my first baby despite significant pain and difficulty. I suspected the reported benefits were due only to confounding, and studies like this (as well as the PROBIT study and discordant sib studies) prove it. Parents can now choose what method works best for themselves and their baby and not have to worry because both bottle and breast have excellent outcomes.

  4. Ruth D
    October 1, 2020 at 9:05 am #

    I’m wondering about the parallels between the narrative around breastmilk being able to improve cognitive function, and the studies done on fish oil which (I believe) has been proven to have an impact. I.e. is there something that a mother could excrete in milk that would be in some way similar, I mean, biologically could influence brain development? I thought the reason humans had supplements and had to eat the fish was that we didn’t produce it ourselves. Not sure – I guess what I’m getting at is, is there even a mechanic by which breastmilk might impact brain or body development other than in terms of what goes into the gut? Rather than all the studies on the outcomes, (PROBIT etc), is there an understanding on what it COULD do? Even the short term digestive benefits that have been seen are just gut flora related. I guess my point is just that I feel like we understand the other workings of the human body on a scientific level enough so that we aren’t arguing about whether smoking is bad for the lungs or not brushing your teeth is bad for the smile. I dunno. Anyone? (Also even Bill Bryson seemed to get it wrong in his book the Body I read someone say).

    • The Bofa on the Sofa
      October 2, 2020 at 9:23 am #

      The studies on fish oil have not held up. Probably not a good comparison

    • rational thinker
      October 5, 2020 at 5:23 am #

      There is still a lot of things we don’t know about the human body, but one day we may with lots more study. It is the things we don’t know that leaves an opening for people to basically just make things up to make money off others. Spreading fear about heath and wellness is a great way to get rich if you are selling things like supplements or “essential oils” which should really be called essential snake oils.

      There is a lot of fear spread around breastfeeding when new moms are told they have to breastfed or baby wont bond to you or formula will give the kid cancer. There are so many lies around what can happen if you don’t breastfeed to list. These people love to demonize the formula industry, but then if you look into why some of these people are so strict about breastfeeding you will discover a money trail that depends on women breastfeeding.

      With breastfeeding if a mom is making enough milk to feed the baby then that baby’s brain development will be fine. The babys brain will also develop normally if mom is not breastfeeding and she has been giving formula from birth and is getting enough formula to fill babys stomach. Then there are cases of babies getting brain damage or dying because mom is breastfeeding but not making enough to fully feed the baby but wont give baby any formula because people told her how bad it is so she is scared to give it to her baby. Or because she just knows people (even total strangers with tell her to her face in public what a bad mom she is for giving baby a bottle of formula. Guilt works.

      A more recent example is the micro biome which scientifically we know very little about, but that wont stop people lying about it and spreading fear and a lot of misinformation. Why do they lie about this? It’s because they have something to sell.

      The reason formula was invented to begin with was because babies were dying.

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