Chronic pain. Understanding of the etiology of chronic pain is growing rapidly as researchers seek to integrate physiologic and psychosocial mechanisms. When nurses assess clients with chronic pain, they should make their assessments using both verbal and nonverbal methods and realize that no one instrument is comprehensive enough to be used alone. The key to successful treatment of these difficult clients lies in the use of a comprehensive approach that takes the client seriously and integrates both physiologic and psychosocial approaches. 