Researchers have shown that children’s level of intelligence may be reliant on how long their mothers breastfeed. The association between breastfeeding and higher scores for some cognitive markers was significant even when accounting for factors such as their mothers’ economic status and intelligence. In a large-scale study, a team from Oxford University showed that these factors had “only a modest” effect on children’s cognitive scores from 9 months to 14 years.

Currently, the World Health Organisation advises that breastfeeding, where a mother feeds her baby milk from her breast, is one of the most effective ways to ensure her child’s health and survival, giving them a head start in life.

Similarly, numerous studies have shown that breastmilk is the ideal food for infants because it’s highly nutritional and a way to pass on antibodies. Consequently, helping to protect against many common childhood illnesses.

Scientists also suspect a strong correlation between breastfed children and their cognitive development, with breastfed children scoring higher on verbal and spatial cognitive tests than their non-breastfed peers. Plausible causal links suggest that the cornucopia of fatty acids, minerals, and vitamins in breast milk provides an enhanced foundation for neurodevelopment.

Factors that can mar and distort study results

Despite the numerous studies to back these claims, a strong relationship is still unclear between how high children score on cognitive test scores and the duration a mother breastfeeds her infant. The actual cause is harder to discern because a mixture of other variable factors, known as confounders, can also affect test scores.

For instance, a child’s increased intellect or cognition could be explained by other characteristics. These could include how long the mother breastfed the infant or if the household is multi-lingual, or the family’s amount of income. Indeed, these confounders can also improve a child’s intellect.

After all, it would be inaccurate to claim that a child’s environment does not directly affect every aspect of their early plasticity, development, and growth, with a mind-boggling amount of variables shaping a child’s physicality and intellect as they grow.

Needless to say, these multiple factors often distort study outcomes as it becomes unclear whether just one of them is responsible for improving cognitive scores in children or whether these confounders are working together unevenly to affect the scores. Whatever the case, it’s easy to see how these ever-convoluted cycles of variants often mar study results.

Investigating how influential a child’s environment is on their intellect

To wade through the countless possible outcomes, researchers analyzed data on over 7,855 children born between 2000 and 2002. The team acquired the statistics from the UK Millennium Cohort Study, which subjected the children to cognitive tests until age 14. Likewise, the children’s mothers also underwent cognitive and socioeconomic evaluation as part of the investigation.

By doing this, the team was able to provide more explicit outcomes, showing that breastfeeding duration was the most heavily weighted factor when improving children’s cognitive scores at ages 5 through 14. Their findings remained unchanged even after integrating confounders such as the mother’s socioeconomic position and intelligence into the new study, published in the open-access journal PLOS ONE.

“Children who were breastfed for several months tend to get higher scores in cognitive tests in comparison with children who were never breastfed. However, it is still not clear whether​this relationship means that breastfeeding causes improvements in cognitive development or if it is due to certain characteristics of the mothers,” study co-author Dr. Reneé Pereyra-Elías, Nuffield Department of Population Health, University of Oxford, wrote to ZME Science in an email.

“In developed nations, like the UK, mothers from more socioeconomically advantaged backgrounds and mothers who score higher in cognitive tests are more likely to breastfeed their babies for several months. Some scientists argue that the relationship between breastfeeding and cognitive development is due to these factors. In our study, after accounting for the differences in socioeconomic circumstances and maternal cognitive ability, longer breastfeeding durations are associated with higher cognitive scores in children, even until age 14,” he adds.

Can a child’s environment cancel out the benefits of breastfeeding?

The study is one of the largest to analyze the effects of the duration of breastfeeding and multiple confounders that can influence the socioeconomic position (SEP) of the mothers within society. In this case, the team investigated the effect of the mother’s educational level, occupation, and combined income and savings on the cognition scores of their children and their SEP.

The children underwent verbal cognition tests at ages 5, 7, 11, and 14 and spatial cognition tests involving manipulating and memorizing objects to complete a task at ages 5, 7, and 11. The study also saw the mothers grouped according to their confounders, including socioeconomic characteristics and maternal cognition based on a vocabulary test.

Next, the team compared cognition test results from children whose mother’s breastfed them against those whose mother’s breastfed them for a long duration, as well as those whose mother’s did not breastfeed them at all. The researchers did not include SEPs in this initial comparison. These unconfounded data found that a longer breastfeeding duration of six months and over was associated with higher verbal and spatial cognitive scores at all ages.

The authors confirmed that even after adjusting for the mother’s variable SEP, children who were breastfed for longer scored higher in cognitive measures up to the age of 14 than children whose mother’s did not breastfeed them.

In a statement to ZME Science about their results, Dr. Pereyra-Elías explains, “Some women have difficulties breastfeeding or continuing for as long as they want to, and others choose not to breastfeed. It is important to remember that the potential gains in cognitive ability among children breastfed for several months would be equivalent to just 2-3 IQ points (in the usual IQ scale, in which the average is 100). However, if a whole population, on average, increases their IQ by 2-3 points, we could see important differences. It is important that women who want to breastfeed their baby are given appropriate support to help them do so.”

Unstandardized factors may cause problems in future studies

However, the team does realize that their study had some limitations. These mainly involve large numbers of confounders which can be defined in many different ways, producing an unstandardized factor, if you will. Basically, what constitutes the correct test and definition for maternal intelligence where the mother does not fulfill the educational aspect of the criteria?

For example, their paper explains that maternal cognitive tests in the study “could be affected by further education and might not necessarily reflect broader intelligence.” But they stress that they used multiple defined testing strategies from past studies to ensure their tests comprised both of these elements. The researchers noted that future studies should host maternal cognition tests at regular intervals, adding that these “multi-dimensional” evaluations should begin at the start of the study in concert with tests on children.

Renee carries on, “While we looked carefully for other reasons for the relationship we observed, it is possible that there are other potential explanations that couldn’t be examined.”

Stressing, “Our study does not provide a definitive answer to this research question. We recommend that future studies try to replicate our findings in different populations. Our study does highlight that it is important to take account of other characteristics, including both socioeconomic circumstances and measures of maternal cognitive ability, to get a truer picture of the relationship between breastfeeding and cognitive development.” 

The team suggests “that the role of breastfeeding on the child’s cognitive scores should not be underestimated,” and that “all future studies” should ensure the inclusion of multiple related confounders such as “socioeconomic factors and maternal intelligence.”

They conclude that “breastfeeding should continue to be encouraged,” as increasing a child’s intelligence is only one of the many improvements it provides.