As many as half of all people hospitalized for surgery or other procedures to treat blocked heart arteries develop depression, according to a report in Wednesday's Journal of the American Medical Association.

Doctors believe the depression is brought on by the mental stress of facing serious illness, or perhaps by microscopic damage done to the brain by the surgery itself. For some patients, the depression is a new thing; for others, it may have been present beforehand.

It may have played a role in the apparent suicide of a Maryland publisher and former diplomat whose body was found earlier this month after he went out sailing on the Chesapeake Bay. The family of Philip Merrill said that he had undergone heart surgery more than a year ago and had become fatigued and unmotivated.

The good news for the more than 71 million Americans suffering from some type of cardiovascular disease is that not only is depression treatable, but more than half of patients respond to initial drug treatment and 80 percent eventually respond to at least one antidepressant, research says.

Dale Briggs knew something was wrong, even though his heart valve surgery had gone all right. An avid reader, he couldn't concentrate on books, couldn't sleep, couldn't eat.

"I was having a lot of symptoms that I didn't even relate to depression," said Briggs, 60, of Clovis, Calif. But glancing at a list of symptoms in his doctor's office, he realized he had all of them except suicidal thoughts.

Drugs soon had Briggs back on his feet. He now helps run Mended Hearts, a support group that hopes to keep fewer heart patients from going through what he did.

Guidelines advise doctors to look for depression in heart patients, and simple questionnaires are available to help them do this, but specialists say that not enough doctors are checking for this problem.

"It's something that's very under-recognized," said Dr. Mary Whooley, an associate professor of medicine at the University of California, San Francisco, who wrote the JAMA report about depression in heart patients.

Depression is present in one of five people with coronary heart disease and in one of three with heart failure — far more than the 1 in 20 in the general population who have it, Whooley wrote.

Depression raises the risk of developing cardiac problems. But even people who were not depressed beforehand can develop "situational depression" when faced with a health crisis or major surgery. "The stress of the illness is a factor," Whooley said.

Also, studies have shown that after bypass surgery, microclots can travel to a patient's brain and cause problems that can include depression, said Dr. Cara East, medical director of the clinical cardiovascular research center at Baylor Heart and Vascular Hospital in Dallas.

Few illnesses are as dramatic or frightening as heart problems, said Wayne Sotile, a Winston-Salem, N.C., psychologist who has written a book on surviving heart disease. Women may be at higher risk of becoming depressed because they typically are nurturers and get less family support when they are in need of care, he said.

Sotile said hundreds of patients have told him they thought about suicide after developing heart problems.

Treating depression can have physical benefits as well, specialists say. Depressed people are less likely to exercise or regularly take their medication — things that can prevent heart problems from getting worse.

Most antidepressants help make the blood less likely to clot, which may help prevent a recurrence of cardiac problems, said Dr. Ranga Krishnan, head of psychiatry at Duke University Medical Center and a consultant for the Depression and Bipolar Support Alliance.

The first step is recognizing the need for treatment, East said.

"In our culture there's a big denial," East said. "People think that you can just control your mind, and you can't."