Breastfeeding Doesn't Make Your Kid Smart. You do.

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If you google “breastfeeding”, you will be bombarded by articles touting the benefits of this most natural of nourishment choices. From the economic savings, to the more pleasant fecal odor, mothers are encouraged that “breast is best”.

Among the benefits frequently touted are those associated with IQ.  I saw this article linking breastfeeding and higher IQ on CNN.com a couple of years ago:

Mothers want to do what is best for their babies, and the pressure in this arena can get intense. In fact, many mothers report significant anxiety associated with the pressure to breast feed.

And women who are unable to breastfeed can be pushed deeper into depression because of that.

And here's a little secret. There have been no randomized trials of breastfeeding. Ever. And we all know that a lot of factors go into the decision to breastfeed, and for how long. In other words, breastfeeding may be a proxy for any number of healthful behaviors, or for socioeconomic status. The question is: Does breastmilk make your kids smart? Or do moms who choose to breastfeed have smart kids?

In response to this question, we have this article, appearing in the journal Pediatrics.

The study looked at 9,854 children from the Growing Up in Ireland infant cohort. These kids were followed from 9 months to 5 years of age. During that time they had multiple neurocognitive and other assessments, and moms were asked about their breastfeeding history.

Right off the bat, you see huge differences in baseline characteristics between moms who breastfeed and those who don't.

This table shows you the amount of confounding we have in studies like this.  Women who breastfed were much more likely to have a resident partner, were higher educated and older. Roughly a quarter of women who breastfed had a smoker in the dwelling during pregnancy compared to 42% of those who didn't breastfeed. And, as anyone with more than one kid can attest, the more siblings in the dwelling, the less breastfeeding happens.

Now, since breastfeeding is a proxy for so many things, it will be no surprise to find that, unadjusted, breastfed kids were better at problem solving, vocabulary, and had better conduct.

But once the kids were matched on all those baseline variables, those relationships disappeared.

When they looked just at women who breastfed for more than 6 months, there was a bit of signal that there was reduced hyperactivity in the kids at age 3. But it disappeared by age 5.

t=Treatment, ie breastfeeding

c=Control, ie no breastfeeding

***p<0.05

In other words, if you are a women who chooses not to breastfeed, or can't breastfeed for some reason, don't feel like you are betraying your child's future. Breastfeeding is great. It's cheap, it helps you lose weight, and it has some antibodies in there. But when it comes to childhood development, it is the loving bond of a mother and infant, perhaps manifested in breastfeeding, but not mediated by breastfeeding, that leads to good development.