March 27, 2017 3:44 pm
Updated: March 28, 2017 8:00 am

Reality check: Does prolonged breastfeeding make your child smarter?

WATCH: Does this new study mean that breast is no longer "best"? Experts chime in.

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Breastfeeding is known to have many health benefits for babies, like reducing a child’s risk of obesity, for example. But can mother’s milk have an effect on a baby’s intelligence and behaviour later in life?

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For years, researchers have debated as to whether or not breastfeeding had that capability. However, new research out of the University College Dublin says that breastfeeding does not have such benefits on long-term cognitive development.

The study, which was released Monday, looked at 8,000 families in Ireland. When kids reached ages three and five, they took standardized tests to measure their cognitive abilities. And while breast-fed kids scored slightly higher, it wasn’t by much, lead author Lisa-Christine Girard tells NPR.

READ MORE: Breastfed kids more likely to recover from stuttering: study

“But [the difference] wasn’t big enough to show statistical significance,” she says. “We weren’t able to find a direct causal link between breastfeeding and children’s cognitive outcomes.”

There are many factors that can impact and shape children’s development, Girard says.

According to Girard, mothers who breastfeed tend to have higher levels of education and are less likely to engage in risky behaviours (like smoking). Other factors include IQ and a child’s home environment.

When researchers first looked at the data without accounting for variables, they saw that breastfeeding was linked to better cognitive development.

However, once they took socio-economic variables into account, breastfeeding by itself didn’t seem to play a role.

One thing researchers did find was that children who were fully breastfed for six months or more had a lower parent-rated score for hyperactivity – but only until age three. They say that breastfeeding for longer periods might help reduce such hyperactivity for kids who show mild to moderate levels in the short term, but these benefits are not seen in the medium term.

For Dr. Catherine Pound, the study is interesting but should not be considered as the final word on the matter.

“It’s certainly worth discussing,” says Pound, an assistant professor at the University of Ottawa and paediatric physician and researcher at the Children’s Hospital of Eastern Ontario (CHEO). “But I only think it’s a study that should be added to the body of literature that exists. I do have to say that I found the results a little bit surprising because we already have so many studies showing very clearly that breastfeeding does have an impact on IQ and cognitive functioning.”

One of those studies comes from McGill University in 2008 which looked at 14,000 children for six-and-a-half years.

Researchers of the study say they found the strongest evidence linking prolonged breastfeeding to increased IQ in children.

They did this by separating participating mothers into two groups: the first group was part of an intervention program that encouraged prolonged and exclusive breastfeeding, and the other without such a program and encouragement. This, researchers say, allowed them to measure the effects of breastfeeding on children’s cognitive development without bias and without knowing factors like the mother’s intelligence.

READ MORE: When is a child too old to breastfeed?

When researchers followed up with the children years later, they gave them an IQ test that included subjects like reading, writing, math and more.

The study found that the children of mothers who prolonged breastfeeding had higher scores.

“The effect of breastfeeding on brain development and intelligence has long been a popular and hotly debated topic,” says Dr. Michael Kramer, co-author of the McGill study, in a statement. “While most studies have been based on association, however, we can now make a causal inference between breastfeeding and intelligence – because of the randomized design of our study.”

And the fact that researchers at the University College Dublin decided to forego a randomized approach is where the study fell short, Pound says.

“This is an observational study and they do try to go around that by using a statistical technique called propensity scoring matching – which is good and helps a little bit, but it’s not the same as a randomized style which really decreases all possibility of bias that you can find with observational studies,” Pound explains.

It is important to note though that researchers did recognize this limitation in their study.

Girard tells NPR: “This has been a debate for over 100 years, and we’re working hard to understand the complete picture.”

The study appears in the April issue of Pediatrics. 

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