Steve Cole of the University of California, Los Angeles, School of Medicine and Gregory Miller of the University of British Columbia said when a person injures a knee, it becomes inflamed -- the body's natural and protective response to injury -- but when a person experiences psychological trauma, this type of chronic inflammation can be destructive.
The researchers recruited a large group of female adolescents who were healthy, but at high risk for experiencing depression. The volunteers were tracked for 2.5 years and measured for C-reactive protein and interleukin-6, two types of inflammatory markers. Their exposure to childhood adversity was also assessed.
In addition, among subjects with previous adversity, high levels of interleukin-6 forecast risk of depression six months later.
The study, published in Biological Psychiatry, found the subjects without childhood adversity had no coupling of depression and inflammation.
"What's important about this study is that it identifies a group of people who are prone to have depression and inflammation at the same time," Miller said in a statement. "That group of people experienced major stress in childhood, often related to poverty, having a parent with a severe illness, or lasting separation from family. As a result, these individuals may experience depressions that are especially difficult to treat."