Image caption Experts studied the physical and mental health of 6,000 people over several years

The combination of depression and coronary heart disease in a patient could be much more deadly than either condition alone, researchers say.

French and British experts say people with both conditions could be four times more likely to die from heart or circulatory disease.

The study, in Heart journal, tracked the mental and physical health of 6,000 middle-aged people over five years.

Experts said doctors must pay more heed to depression in heart patients.

Experts from the University College London and the University of Versailles followed the health of just under 6,000 male and female civil servants for an average of five and a half years.

The volunteers were taking part in the British Whitehall Study II, which is looking at social and economic factors in long-term health.

Exercise

They found people with heart disease alone had a 67% higher chance of dying from any cause than those without either heart disease or depression.

But the combination of heart disease and depression tripled the risk of death from any cause and quadrupled the risk of dying from cardiovascular disease.

Amy Thompson, a senior cardiac nurse at the British Heart Foundation, which partly funded the study, said: "This study builds on previous research which suggests that depression is linked to coronary heart disease.

"Enjoying regular exercise and eating a healthy, balanced diet can help if you are feeling low - so, good news for your mental health as well as your heart health.

"Whether or not you have heart disease, if you feel depressed it's essential to talk to your doctor."