Cortisol, a stress hormone increases in children who witness constant parental conflicts.

It has already been accepted that such  children are prone to psychological problems. But the biological reasons behind them have now been deciphered.

Researchers at the University of Rochester, the University of Minnesota and the University of Notre Dame  conducted a study on 208 6-year-olds and their mothers.

The aim of the research was to find out if children who showed specific behavior patterns of reacting to conflict also exhibited some  changes in cortisol levels during a simulated telephonic  argument between their parents.

"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.

Prof. Davies 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."