Depression in people may accelerate the heart conditions by releasing the levels of a protein that causes inflammations.
In a study of 32 people with heart failure, the 14 patients who felt the most depressed had nearly twice the levels of this protein in their blood.
The protein, tumor necrosis factor alpha (TNF-alpha), is one member of a large family of proteins called cytokines, chemical messengers that are mobilized when the body is injured or has an infection. These cytokines often cause inflammation in their effort to repair an injured or infected area of the body. In the case of heart failure, this inflammation makes it even more difficult for the heart to pump blood. (Heart failure is a disease in which the heart loses the ability to pump blood with normal efficiency.)
People with heart failure typically have much higher TNF-alpha levels than people without the disease.
But depression seems to make levels of this cytokine even higher, which is bad for patients. The study's results appear in a recent issue of the American Heart Journal.
The researchers had recruited 32 patients from the heart failure clinic at Ohio State. The participants answered the 21-question Beck Depression Inventory, a tool that physicians and scientists use to measure symptoms of depression. The researchers drew blood samples from each patient. From these samples they evaluated levels of three cytokines: TNF-alpha, interleukin-6 (IL-6) and interleukin-1beta (IL-1beta). Previous research by other scientists has shown that the three cytokines, which all cause inflammation, are elevated in patients with heart failure.
Indeed, all of the patients in the study had higher-than-normal levels of each cytokine. However, TNF-alpha was still markedly higher in patients who reported feeling depressed on a regular basis.