Children who get distressed because of constant parental conflicts have higher levels of cortisol, a stress hormone, according to scientists.
While it is known that children who witness their parents fighting are prone to psychological problems, the biological responses going on behind these behavioural reactions have now been uncovered.
The study, by researchers at the University of Rochester, the University of Minnesota, and the University of Notre Dame, was conducted on 208 primarily White 6-year-olds and their mothers.
The researchers aimed to find out if children who showed specific behaviour patterns of reacting to conflict also had changes in cortisol levels during simulated telephone arguments between their parents.
For the study, they measured children's distress, hostility, and level of involvement in the arguments, and received reports from the mothers about how their children responded when parents fought at home.
Then, cortisol levels were measured by taking saliva samples before and after the conflicts in the lab.
The findings revealed that children who were very distressed by the conflicts in the lab had higher levels of cortisol in response to their parents fighting.
Children's levels of hostility and their involvement during the arguments weren't always related to their levels of cortisol, the study found.
But children who were very distressed and very involved in response to parental fighting had especially high levels of cortisol.
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, said Patrick T. Davies, professor of psychology at the University of Rochester, who led the study.
He added: 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 has implications for policy and practice: The common practice of judging how well intervention programs are doing based solely on improvements in how children function psychologically may need to be changed to include physiological measures like cortisol levels.
The study is appearing in the November/December 2008 issue of the journal Child Development.