Medical experts have linked depression with a higher risk of heart disease, claiming that as many as one in five heart attacks could be caused by mental illness.

The researchers found that depression may be one of the top risk factors for cardiovascular disease, on par with high cholesterol levels and obesity.

Ahmed Tawakol, a professor of medicine at Harvard Medical School who has conducted research on the connection between stress and heart health, said: “An association between psychological health and disease has been appreciated for centuries.

“However, only over the past decades has mounting evidence suggested that stress and depression may be more than simple markers of heart disease; they might be important causes.”

To discover this, scientists at the Technical University of Munich looked at the mental and physical state of 3,500 Germen men between the ages of 45 and 74 years over a 10-year period.

They found that the risk of fatal heart disease was as high in men with depression as it was in men with high cholesterol levels or obesity. They concluded that around 15 per cent of cardiovascular-related diseases were attributed to depression.

By comparison, around 21 per cent of heart attacks are caused by obesity, while 8.4 per cent are caused by high blood pressure and smoking.

Dr Karl-Heinz Ladwig, a professor of psychosomatic medicine at the Technical University of Munich and the study’s lead author, said: “Our data show that depression has a medium effect size within the range of major, non-congenital risk factors for cardiovascular diseases.

“In high risk patients, the diagnostic investigation of co-morbid depression should be standard. This could be registered with simple means.”