Breastfeeding is of little benefit to early life intelligence and does not affect children's cognitive growth over time, new research at Goldsmiths, University of London has shown.
In a longitudinal study of 11,000 British children, psychologists found that breastfeeding was not reliably related to IQ at age two, suggesting that IQ differences in early life cannot be attributed to whether a child has been breastfed or not.
Breastfeeding was also not related to IQ gains after the age of two, indicating that breastfeeding does not make brains grow better over time.
Dr Sophie von Stumm (Goldsmiths) and Dr Robert Plomin (King’s College London) reported that while girls’ IQs were a little higher than boys before the age of seven, the advantage disappeared by 16.
Data came from the Twins Early Development Study (TEDS) at Kings College London, which originally enrolled 15,000 families. The twins were tested nine times on cognitive ability between age 2 and 16 years, so the researchers could study their growth trajectories in intelligence over time.
The researchers tested the relationship between breastfeeding and intelligence over time in a sample of one twin randomly selected from a pair and replicated their results in the other twin’s sample.
The study design overcomes many limitations of previous studies, in particular because of the large sample size and regular assessments from early life through adolescence.
Dr von Stumm said: “Many researchers have previously investigated whether being breastfed in early life benefits IQ. Such an association is plausible because long-chain polysaturated fatty acids that are present in human breast milk but not animal milk or formula enhance neurodevelopment. However, few of the earlier studies have employed strong research designs that produce reliable results."
Dr von Stumm, who studies the causes and consequences of individual differences in cognitive development, was not surprised to find no association between breastfeeding and IQ. She explains:
"Children - and adults - differ in their cognitive abilities, and it is important to identify factors that give rise to these differences. But comparatively small events like breastfeeding are very unlikely to be at the core of something as big and complex as children's differences in IQ. Instead, children's IQ differences are better explained by long-term factors, for example, children's family background and their schooling.”
Dr von Stumm also cautioned:
“It’s important to keep in mind that while our study does not indicate a link between breastfeeding and intelligence, breastfeeding potentially has other benefits, for example for the development of children's autoimmune system. That said, mothers should be aware that they are not harming their child if they choose not to, or cannot, breastfeed – being bottlefed as an infant won’t cost your child a chance at a university degree later in life."
Breastfeeding and IQ growth from toddlerhood through adolescence by Sophie von Stumm and Robert Plomin was published in PloS One on 23 September 2015.