UNT researcher finds infant stress levels remain high during sleep training

Thursday, May 31, 2012

DENTON (UNT), Texas -- Like many parents, when Wendy Middlemiss' son was a baby, she wondered whether infant sleep training, though hugely popular, was a healthy way to help infants learn to sleep through the night without crying.

She wondered whether this practice, where parents let infants settle themselves to sleep by not responding to their cries, was detrimental to infants' emotional well-being.

When Middlemiss looked for scientific support for the practice of sleep training, she found none. Soon after, she began working to determine whether or not parents should respond to their child's nighttime cries. Her research results were recently published in Early Human Development.

"Infants rely on parents to regulate their emotional states in the first year of life--needing parents to help them when they are upset. Thus, parental non-responsiveness can be detrimental to infants' learning how to calm themselves down when they are distressed," said Middlemiss, an associate professor in UNT's Department of Educational Psychology within the College of Education. "Parents' support of infants when they are distressed, in part marked by parents' emotional availability, can contribute to better quality sleep, as well as better emotional and social skills."

Working with nurses in New Zealand, she began studying infants participating in a hospital-based sleep program. In one of the first infant sleep studies to look at mothers' and infants' physiological stress responses during sleep training, Middlemiss used saliva test kits to study different stress markers, such as cortisol levels, in the babies and their mothers. Her findings indicate that parents might have reason to be concerned with how infants experience sleep training, at least during the initial days of this sleep approach.

"We found that while the practice was successful in helping infants to settle themselves to sleep without crying, infants' physiological stress levels remained very high even when mothers' stress responses were lower," Middlemiss said.

Middlemiss said her research indicates that, at least during the early days of sleep training, prolonged maternal non-responsiveness is associated with continued high levels of infant stress. She notes this could be a concern if infants' levels of stress continued to remain high as their physiological stress responses are developing in that first year. Chronic stress can cause infants to develop an overactive stress response system, which can result in later difficulties regulating social and behavior responses. These difficulties can include attention disorders, anti-social behavior and possibly even obesity.

Middlemiss' study found that during sleep training babies may no longer cry at night even when they are distressed, which results in a disconnect between the baby and its mother.

"Nighttime care is largely based on questions of how often infants wake at night and whether they need attention as they fall asleep. Although parents often prefer to be present when infants fall asleep, because this practice can lead to more waking, the practice is often discouraged. It is important to realize that sleep is different in adults than it is in babies," Middlemiss said. "Further, infants whose parents attend to them when they wake often sleep for the same amount of time during the night because they may wake for shorter periods."

Middlemiss suggests helping parents understand that letting infants cry themselves to sleep may be associated with continued stress.

"There are other ways to help infants settle themselves to sleep that are not associated with prolonged periods of crying, perhaps these would be a better approach for parents who would like their infants to settle themselves to sleep," Middlemiss said.

Dr. Douglas A. Granger of Johns Hopkins Center for Interdisciplinary Salivary Bioscience Research, Wendy A. Goldberg of the University of California, Irvine, and UNT graduate student Laura Nathans were co-investigators on the project.

UNT News Service Phone Number: (940) 565-2108

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