WEDNESDAY, Nov. 19, 2008 (HealthDay News) -- Bickering parents and poor caregiver relationships each increase levels of the stress hormone cortisol in children, new studies say.
The two studies, published in the November/December issue of Child Development, show the biological effects stress has on children in these common situations.
Long-term or frequent rises in cortisol can have negative health consequences. Research with animals and people suggest that secure relationships help prevent cortisol rises in children confronted with stress.
The first study, which looked at 191 full-time day-care children, found that many preschoolers experience increasing levels of cortisol throughout the day, the opposite of how the hormone is produced in most humans.
Children in classrooms with around 10 children were more likely to experience normal cortisol decreases from morning to afternoon; however, those in classes with closer to 20 children tended to have greater increases in cortisol across the day.
The study, by Washington State University, Auburn University, Washington State Department of Early Learning, and Pennsylvania State University researchers, also found that children with more clingy relationships with their teachers also had greater cortisol increases throughout the day. Those with poorer relationships with their caregivers also experienced a hormone boost after one-on-one interactions with the caregiver.
"This study sheds additional light on an as yet incompletely understood phenomenon among many young children attending full-day child care," study author Jared A. Lisonbee, an assistant professor of human development at Washington State University, said in a news release from the journal's publisher. "Additionally, the study begins to situate child care-cortisol research in the context of a broader literature on the role of relationships in shaping how children function and how they react to stress."
In the second study, higher cortisol levels were found in children distressed by their parents' fighting.
Children who become very upset when their parents fight are more likely to develop psychological problems. But little is known about what happens beyond these behavioral reactions in terms of children's biological responses. A new study has found that also have higher levels of cortisol.
The study, by researchers at the University of Rochester, the University of Minnesota, and the University of Notre Dame, looked at more than 200 6-year-olds and their mothers. The children's levels of hostility and their involvement during the arguments didn't always link to their levels of cortisol, but those who were very distressed and very involved had especially high levels of the stress hormone.
"Our results indicate that children who are distressed by conflict between their parents show greater biological sensitivity to conflict in the form of higher levels of the stress hormone, cortisol," study leader Patrick T. Davies, professor of psychology at the University of Rochester, said in a news release from the journal's publisher. "Because higher levels of cortisol have been linked to a wide range of mental and physical health difficulties, high levels of cortisol may help explain why children who experience high levels of distress when their parents argue are more likely to experience later health problems."
The authors suggested that the study could affect future policy and practice. They said physiological measures like cortisol levels may help determine how well intervention programs are doing as well as the common practice of looking for improvements in how children function psychologically.
The U.S. National Library of Medicine has more about stress.