Pain is both a curse and a blessing. At its best, pain serves to warn of real or impending tissue damage. Through its motivational and aversive aspects, pain compels individuals to take action, avoiding a worsening of damage, and/or beginning the process of restoration of damaged tissues. Unfortunately, pain's value as a warning signal is limited, and it may have exceedingly negative consequences. There are many situations, such as cancers, in which an individual can experience extreme and even life-threatening pathophysiology, without the perception of pain. An opposite problem may occur. Some individuals experience pain in the absence of any pathophysiological process, as in the case of somatoform pain disorder. Finally, many patients with tissue damage or a disease process may experience protracted disabling pain, leading to a downward spiral of emotional malaise, decreased physical function, and psychosocial upheaval.
Pain is ubiquitous. As the chapter by LeResche and VonKorff in the present volume demonstrates, pain can strike almost any organ system, and afflicts the young and old alike. The universal and aversive nature of pain has led to rapid development of the field of pain management.
Pain is complex. As discussed in the chapter by Riley and Robinson, pain is no longer considered a simple sensory occurrence. Rather, the most widely accepted current framework for the understanding of pain is now the biopsychosocial model. According to this model, nociception serves as a starting point for a series of events that culminate in the patient's perception of pain and overt pain behaviors. In the process, the pain experience is influenced by a) physical factors involved in pain signal transmission, b) psychological and emotional factors involved in the interpretation of pain signals, and c) environmental factors that provide incentives or disincentives for recovery.
The biopsychosocial model serves as a guide for the current volume. Part I of this volume provides in-depth coverage of some of the major psychosocial factors influencing pain syndromes. Financial and economic factors influencing pain syndromes are discussed in the chapter by Hadjistavropolous. Craig, Hill, and McMurtry both discuss how pain pa-