Breastfeeding May Not Be Important For Children’s IQ

Sophie von Stumm BSc MSc PhD Department of Psychology Goldsmiths University of London London, United Interview with:
Sophie von Stumm BSc MSc PhD
Department of Psychology
Goldsmiths University of London
London, United Kingdom

Medical Research: What is the background for this study?

Dr. von Stumm: At the Hungry Mind Lab (, which I direct, we study individual differences in lifespan cognitive development. In particular, I am interested in factors that influence change in cognitive ability and knowledge. One such factor is breastfeeding, which some previous studies suggested to be associated children’s intelligence and IQ gains while others failed to find a relationship.

Medical Research: What are the main findings?

Dr. von Stumm: For this study, which was published last week in PloS One (link:, data were analyzed from more than 11,000 children born in the UK between 1994 and 1996. The children had been repeatedly assessed on IQ: the first time they were tested on intelligence at age 2, and then again repeatedly throughout childhood, overall 9 times, until the age of 16 years. We found that having been breastfed versus not having been breastfed was not meaningfully associated with children’s IQ differences at age 2 and also not with differences in children’s IQ gains until age 16. That is not to say that breastfeeding may not have other benefits for children’s development but our study strongly suggests that breastfeeding is not important for children’s IQ.  

Medical Research: What should clinicians and patients take away from your report?

Dr. von Stumm: Our study does not have direct policy implications. Notwithstanding, I believe it is important to communicate our findings widely, because mothers in the UK are frequently judged for not breastfeeding — regardless of what their reasons are, while the potential negative consequences of not breastfeeding tend to be overemphasized. This makes many mothers feel inadequate; however, being a new mum is stressful enough without unfounded feelings of guilt. Breastfeeding may have benefits for child development but they don’t include IQ (and this isn’t the first study to demonstrate this in a UK sample). Mothers must not believe that they harmed their child’s intelligence because they didn’t breastfeed.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. von Stumm: Longitudinal studies on the relationship between breastfeeding and IQ suffer two major limitations, and our study is no exception in this. The first problem is the assessment of breastfeeding: In many cases, mothers are asked about if and for how long they breastfed months if not years after the actual event, which can introduce measurement error because of biases in the recall.

The second problem is that of confounding: There are very many variables that affect children’s IQ and there are very many variables that are associated with the likelihood of being breastfed, for example educational, occupational and marital status and parental IQ. Good longitudinal studies, like ours, assess some of these confounders and statistically control for them but it is almost impossible to consider all of them. As a consequence, the possibility remains that any reported association between an exposure variable, like breastfeeding, and an outcome, like IQ, is spurious. I hope that future studies will overcome these two problems.


Breastfeeding and IQ Growth from Toddlerhood through Adolescence

Sophie von Stumm ,Robert Plomin

Published: September 25, 2015 DOI: 10.1371/journal.pone.0138676

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Sophie von Stumm BSc MSc PhD (2015). Breastfeeding May Not Be Important For Children’s IQ