Breastfeeding and IQ

Breastfeeding is VERY politically correct these days.  Mothers who do not breastfeed can be harassed by other mothers over it.  Why?  Because breastfeeding is thought to be  "more natural" and hence better for the baby.  But better in what way? One claim is that is helps the child's IQ.  But the studies have not been very supportive of that. So the latest very extensive study is of great interest.  Abstract below:

Breastfeeding and IQ Growth from Toddlerhood through Adolescence

By Sophie von Stumm &  Robert Plomin

Objectives
The benefits of breastfeeding for cognitive development continue to be hotly debated but are yet to be supported by conclusive empirical evidence.

Methods
We used here a latent growth curve modeling approach to test the association of breastfeeding with IQ growth trajectories, which allows differentiating the variance in the IQ starting point in early life from variance in IQ gains that occur later in childhood through adolescence. Breastfeeding (yes/ no) was modeled as a direct predictor of three IQ latent growth factors (i.e. intercept, slope and quadratic term) and adjusted for the covariates socioeconomic status, mother's age at birth and gestational stage. Data came from the Twins Early Development Study (TEDS), a prospective cohort study of twins born between
1996 and 1994 in the United Kingdom, who were assessed 9 times on IQ between age 2 and 16 years (N = 11,582).

Results
Having been breastfed was associated with a small yet significant advantage in IQ at age 2 in girls (β = .07, CI 95% from 0.64 to 3.01; N = 3,035) but not in boys (β = .04, CI 95% from -0.14 to 2.41). Having been breastfeeding was neither associated with the other IQ growth factors in girls (slope: β = .02, CI 95% from -0.25 to 0.43; quadratic: β = .01, CI 95% from -0.02 to 0.02) nor in boys (slope: β = .02, CI 95% from -0.30 to 0.47; quadratic: β = -.01, CI 95% from -0.01 to 0.01).

Conclusions
Breastfeeding has little benefit for early life intelligence and cognitive growth from toddlerhood through adolescence.

Von Stumm S, Plomin R (2015). Breastfeeding and IQ Growth from Toddlerhood through Adolescence. PLoS ONE 10(9): e0138676. doi:10.1371/journal.pone.0138676

The study is persuasive rather than conclusive.  I think IQ of the mother should have been controlled for.  I made the same criticism of a noted Brazilian study which did find some benefit from breastfeeding.

Another concern is that the measures of IQ used at different ages were not well correlated. They could obviously not be the same but correlations between them as low as .18 are a serious concern.

Overall, however, the general agreement of the studies on the matter leads me to agree that breastfeeding has no effect on IQ.  It may however have other benefits.

Posted by John J. Ray (M.A.; Ph.D.).