The Illness Behavior Assessment Schedule: reliability and validity.

A patient's illness behavior represents an important component of any clinical presentation, and may in itself be pathological. Illness behavior and abnormal illness behavior are not easily evaluated, and considerable disagreement exists as to the criteria for making diagnoses such as "conversion reaction," "hypochondriacal reaction," etc. This paper describes the background, reliability and validity of the Illness Behavior Assessment Schedule (IBAS) which has been developed as a basis for a systematic and standardized approach to illness behavior.