INDIANAPOLIS, Oct. 13 (UPI) -- U.S. researchers found depression leads to elevated levels of an inflammatory protein in the body.
The study, published in Brain, Behavior and Immunity, found depressive symptoms associated with increases over time in interleukin-6, an inflammatory protein that predicts cardiovascular events. The study determined levels of interleukin-6 were not related to later increases in depressive symptoms.
"There is two-way communication between the brain and the immune system, so we had to determine whether activation of the body's immune system sent a signal to the brain to affect mood and behavior or whether the depression activated the immune system," study leader Dr. Jesse Stewart of Indiana University - Purdue University Indianapolis said in a statement. "The link to cardiovascular disease demonstrates that there may be physical as well as mental health reasons to treat depression."
The study involved 263 healthy men and women ages 50-70, who were tested at baseline and again six years later to determine their levels of depressive symptoms and interleukin-6.
Levels of C-reactive protein -- another inflammatory protein -- were also measured but were not found to be related to depression.