Factors in the diagnosis and treatment of chronic pain.

Symptoms are the verbal and nonverbal communicative expressions of experience. At any one time, the symptom is dependent on structural changes, genetic variations, metabolic abnormalities, immunopathic and other disorders, and the totality of social, economic, and situational experience. Complaints of pain may vary with time depending on the interaction of these features in a manner not directly related to the intensity of a noxious stimulus.