Hypochonriasis (or hypochondria, sometimes referred to as health phobia) refers to an excessive preoccupation or worry about having a serious illness. Often, hypochondria persists even after a physician has evaluated a person and reassured him/her that his/her concerns about symptoms do not have an underlying medical basis or, if there is a medical illness, the concerns are far in excess of what is appropriate for the level of disease. Many people suffering from this disorder focus on a particular symptom as the catalyst of their worrying, such as gastro-intestinal problems, palpitations, or muscle fatigue.