Illness behavior.

The term illness behavior was introduced by Mechanic and Volkart to describe the individuals' different ways to respond to their own health status. Pilowsky's concept of abnormal illness behavior encompasses several clinical conditions characterized by a maladaptive mode of experiencing, perceiving, evaluating and responding to one's own health status. The concept of somatization was criticized because it implies the presence of psychological distress or an underlying psychiatric disturbance when an organic cause for somatic symptoms is not found. Thus, more atheoretical terms , such as functional somatic symptoms and medically unexplained symptoms, were introduced. Both Kellner's Symptom Questionnaire and Derogatis' Symptom Checklist-90 include a scale for somatic symptoms, and other questionnaires were specifically designed to measure their frequency and severity. Kellner's Illness Attitude Scales appear to be the gold standard for the measurement of the hypochondriacal spectrum, which includes several clinical conditions, such as nosophobia, thanatophobia and health anxiety. The assessment of illness denial should consider that a certain degree of denial may sometimes prevent patients from overwhelming psychological distress resulting from life-threatening or stigmatized diseases. Denial may concern both physical and psychiatric symptoms. Specific instruments are available for both types of denial. The cognitive and emotional representations developed by subjects when they have to cope with an illness or a perceived health threat are subsumed under the concept of illness perception and may be assessed by the Brief Illness Perception Questionnaire.