Heart failure patients who are even mildly depressed may have a poorer prognosis than others with the heart ailment, researchers reported Monday.

Their study of more than 1,000 adults with heart failure found that those who were suffering from Depression - or even “sub-depressive” symptoms - were more likely than other patients to die over the next seven years.

Compared with patients without depression, men and women who were classified as having depression on a standard screening test were 44 percent more likely to die over the study period.

But the risk was even greater when the researchers included heart failure patients who were just shy of the cut-off point used to define depression.

Heart failure is a chronic condition in which the heart is unable to pump blood efficiently enough to meet the body’s needs. When the heart cannot properly fill up with blood or pump it out with enough force, fluid builds up in the lungs and throughout the body, leading to problems such as breathlessness, fatigue and swelling in the extremities.

Heart failure usually results from an underlying condition, such asCoronary Artery Disease-in which plaque build-up in the arteries impedes blood flow to the heart-high blood pressure or cardiac-muscle damage from a Heart attack.

Past research has shown depression to be common among people with heart failure, with a recent study putting the prevalence at about 20 percent.

The new findings point to the impact that depression may have on a patient’s long-term prognosis, said Dr. Wei Jiang of Duke University Medical Center in Durham, North Carolina.

She presented her team’s findings at an American College of Cardiology meeting being held this week in Orlando.

Heart failure patients are not routinely screened for depression, Jiang told Reuters Health in an interview, and symptoms of mild depression may be hard to recognize - particularly since heart failure and depression share some features, such as fatigue and appetite loss.

“So doctors may think that it’s in the patient’s heart, not the mind,” she said.

But even if doctors did screen heart failure patients for depression, it’s not yet clear that treating the depression would improve patients’ outlook. Jiang said she and her colleagues are now studying that question, looking at whether antidepressant therapy improves the long-term outcomes of heart failure patients with major depression.

The current study included 1,005 heart failure patients treated at Duke University Hospital for cardiac complications. During their hospitalization, the patients were given a standard screen for depression known as the Beck’s Depression Inventory, or BDI. In general, a BDI score of 10 is used as the threshold for mild depression.

Jiang’s team found that patients who scored 10 or greater were 44 percent more likely to die over the next seven years than patients with lower scores. To see if there were effects at an even lower threshold, the researchers compared patients with a BDI score of 7 or higher against patients with lower scores. This time, the risk of death was 51 percent greater in the higher-scoring group.

Patients with BDI scores just below 10 would not be considered to have clinical depression, Jiang said, but their symptoms may be significant enough to have an impact on their prognosis.

Exactly how depression raises death risk in heart failure is not fully clear, but Jiang said there are several theories on the relationship.

For example, research suggests that depression can increase the activity of platelets, cells that promote blood clotting. Depression could also have effects on the immune system or the sympathetic and parasympathetic nervous systems, which help regulate the heart’s response to everyday stresses.

Whatever the reason for the connection, Jiang said the new findings highlight the potential importance of depression in how well heart failure patients fare.

“The message to both patients and physicians,” she said, “is to pay attention to even mild levels of depression.”