Does breastfeeding enhance the intelligence of a child?

Breastfeeding is beneficial for the brain of children, is it true?
This opinion has been supported by some researchers for many years. However, to prove the precise effect of breastfeeding on the development of children is quite difficult. To perform a randomized controlled trial is almost impossible for the reason of ethical issue. The results of the experiments with animal models is hardly adapted to human. Moreover, this kind of discussion tends to cause emotional conflicts.

Recently, an article published in JAMA pediatrics, one of the top journals in this region, has become the center of public attention. Maybe the birth of a royal baby in the UK has enhanced the public concern to this matter.

Mail Online: Breastfeeding 'can enhance a child's IQ': Longer a mother chooses to feed baby the better their intelligence scores aged seven

Live Well: Breastfeeding boosts intellect in kids

According to this article, a cohort study showed that the mean IQ score of the breastfed children is higher than the bottle fed children by 4 points at the age of 7.
One of the originality of this article is that several possible biases were excluded with statistic techniques.

Infant Feeding and Childhood Cognition at Ages 3 and 7 Years: Effects of Breastfeeding Duration and Exclusivity.

Unfortunately, I have no account of JAMA pediatrics. So I could not read the whole article. Thorough investigation is needed to evaluate an academic article. Therefore, it is difficult for me to make any comments. Nonetheless, there is a quite simple question about this result.

How much important is the 4 points of IQ?

To be honest, IQ is only one standard. And, IQ is not a fixed number for a person. If you took multiple examinations to evaluate your IQ, the results would be varied. This difference may be statistically significant. However, the clinical value of the result is unknown.

It is also possible that some biases are not able to be evaluated properly. It is impossible to eliminate all of confounding factors with post hock analysis.

By the way, there are 412 articles found at the PubMed, a standard portal site of medical articles, with the keywords “breastfeeding” and “Intelligence”. It means that the relationship between them is concerned in pediatricians to some extent. In contrast, 206 articles are found with the keywords “influenza” and “schizophrenia”, indeed 14,742 articles about “cancer” and “fish”.