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Breastfeeding May Lower Stress In 5-Month Old Babies

A black mother holds her baby to her breast to breastfeed. Woman is wearing a green t-shirt and baby a blue onesie.
Office on Women's Heath

A Utah researcher wanted to know more about maternal caregiving, such as breastfeeding, and if it could lead to lower levels of stress in five-month-old babies. 

"We were interested in whether maternal caregiving behavior, in this case, breastfeeding could also induce epigenetic effects in the baby," said Elizabeth Conradt, an assistant professor in developmental psychology at the University of Utah. "Epigenetics is how the environment can affect which genes are expressed. Our genotype does not change throughout our lifespan but our epigenome can, and it is influenced by how an environment can turn on or off certain genes." 

Conradt and her collaborators in Rhode Island researched how breastfeeding influenced the production of the stress hormone cortisol, which is the hormone responsible for the flight-or-fight instinct.

"The way that we looked at cortisol reactivity was in response to the still face paradigm, which is an experimental paradigm in which the mom first plays with the baby. And then we ask her to put on a still face or a poker face, where she has a flat affect and she doesn’t respond to the baby, she doesn’t talk to the baby, and this lasts a maximum of two minutes," Conradt said. "This is a stressor, a mild social stressor for the baby, and it is a way for us to understand how that baby’s stress response system is developing."

Conradt found that mothers who breastfed their babies at higher rates showed lower levels of systematic stress.  

"So we found that breastfeeding, and this was either nursing directly from the breast or bottle feeding with breast milk, was associated with epigenetic effects in the baby at five months of age, and these epigenetic effects were related to the degree of the stress hormone cortisol was in the baby," Conradt said. "We think this could be related to a baby that is more reactive in response to changes in the environment or changes in mom’s mood."

According to Conradt, there is still a lot of research to do, but she says this study further emphasizes the importance of an early mother-infant relationship.