Dr. Angelos Halaris of the Loyola University Medical Center near Chicago said 40 percent to 60 percent of heart disease patients suffer clinical depression and 30 percent to 50 percent of patients who suffer clinical depression were at risk of developing cardiovascular disease.
The body's immune system fights stress as it would fight a disease or infection. The immune system produces proteins cytokines, including interleukin-6.
Initially, this inflammatory response protects against stress, but over time, a chronic inflammatory response can lead to arteriosclerosis -- hardening of the arteries -- and cardiovascular disease.
It's a vicious cycle: depression triggers a chronic inflammation, which leads to heart disease, which causes depression, which leads to more heart disease, Halaris said.
In his most recent study, Halaris and colleagues found that an inflammatory biomarker, interleukin-6, was significantly higher in the blood of 48 patients diagnosed with major depression than it was in 20 healthy controls.
Halaris presented the findings at a joint congress of the World Psychiatric Association and International Neuropsychiatric Association in Athens. At the congress, Halaris formally proposed creation of a new psychocardiology sub-specialty.