Do you think that breastfeeding affects the later behavior of children? A study published May 9, 2011, in the Archives of Disease in Childhood reports just such a conclusion. The research, led by Katriina Heikkilä of the Finnish Institute of Occupational Health, involved more than 10,000 mother–child pairs in the U.K. Based on the team’s findings, children who breastfed for four months or more were less likely to score poorly on a parent-completed behavioral questionnaire at age 5 years. The study also found that abnormal scores on the questionnaire were more common for children who were born pre-term.
All of the children are participants in the Millennium Cohort Study of about 19,000 infants born in 2000–2001 (hence the “Millennium Cohort”) in the UK. Because the researchers took data in the moment—right when women may still have been breastfeeding—and then followed participants through the years, the study didn’t rely on distant memory for data. The investigators asked the moms about breastfeeding when the children were 9 months old, then had parents fill out a questionnaire about behavior when the children were 5 years old. They divided the children into two groups at the beginning of the study based on whether they’d been born full term or pre-term.
When the children turned five, the parents completed the Strengths and Difficulties Questionnaire, rating such behaviors as consideration for other people’s feelings, losing temper, sharing readily, fidgeting a lot, or lying and cheating. Parents had to rank each behavior as “not true,” “somewhat true,” or “certainly true.” While 12% of full-term children had abnormal scores on the questionnaire, 15% of pre-term children did. When the researchers took breastfeeding into account, full-term children who’d been at the breast for at least 4 months were about a third less likely to have an abnormal questionnaire score than children who’d not been breastfed at least that long. Pre-term children who were breastfed at least 4 months seemed to have better scores than pre-term children who weren’t, but the researchers found the data unclear.
What might drive parent-rated better behavior in children breastfed at least 4 months? It’s difficult to speculate, as this study simply shows a mathematical relationship between parent-reported breastfeeding and parent-reported child behavior 4-plus years later. No one can say what component of breastfeeding might influence a child’s later behavior—or a parent’s perception or report of that behavior.
If the association is real, it could have to do with the close physical contact of breastfeeding, components of the breastmilk, or traits of women who choose to breastfeed. One way to distinguish breastmilk from physical contact would be to include children like my youngest, who had breastmilk (thanks, Medela pump!) but who had to take it from a bottle because he could not nurse. How’s his behavior? No better, no worse compared to his two (mostly) breastfed brothers. How that would fit in with the conclusions of Katriina Heikkilä and colleagues about breastfeeding and behavior remains unclear: Did he breastfeed…or didn’t he?
Dr. Emily Willingham came to EarthSky from The Biology Files. Her background includes a PhD in biological sciences, a bachelor's degree in English, and a published book: The Complete Idiot's Guide to College Biology. She is a scientist, writer, editor, teacher, autism & ADHD parent, and "all around opinionator." Says Emily: "Got an English BA & biology PhD, & I'm not afraid to use them, often together."