What Is A Psychosomatic Illness?

Traditionally it was felt that a psychosomatic illness was one which was purely 'in the mind' and did not actually exist.  However, recently, doctors have begun to understand that a psychsomatic illness is one where the body is affected by the mind, so the mind may cause the disease, but the physical symptoms are real.
So for example, a person may experience an asthma attack after a very stressful experience.  But the asthma attack is real.
The term is derived from the Greek words psyche which means soul and soma which means body.  So in this way the soul influences the body.
A psychsomatic illness is different from an illness which is purely in the mind.  For example, a person may be convinced that they have cancer even when they do not.   This is a mental illness, not a psychosomatic illness.  For it to be psychosomatic there has to be a combination of stress/mental distress and physical symptoms.