The psychological problems associated with kids who see their parents fighting are well known.

However, little is known about the physical effects from moms and dads behavioral problems.

A study by the University of Rochester, the University of Minnesota, and the University of Notre Dame looked at children who were exposed to conflict at home.

Saliva swabs showed children exposed to family in-fighting had higher levels of a stress hormone known as cortisol.

Lead researcher Patrick Davies said "High levels of cortisol have been linked to a wide range of mental and physical health difficulties."

He said the elevation of this hormone may help explain why children from these households go on to develop health problems.

They were more sensitive to conflict than children from other situations, the research group discovered.

According to the National Institutes of Health, cortisol levels rise and fall naturally during the day, peaking around 06:00 to 08:00 and bottoming out about midnight.