Pain is a complex, perceptual experience, defined as an “unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”1 One of the critical developments in the past several decades in pain research is the progress in our understanding of the multifactorial, biobehavioral mechanisms involved with chronic pain.2 Research has consistently shown the importance of using multimodal approaches to treat patients with chronic pain3 because monotherapies appear to provide less than optimal relief.4 These developments have pointed to various psychological factors—cognitive, emotional, and behavioral—as significant contributors for pain modulation and pain-related disability.5
The main objective of this chapter is to review the various psychological factors relevant to the experience of pain. As a background, it is important to consider how we conceptualize pain. Our view of pain will influence our evaluations of patients who report pain and the nature of the interventions that we use to treat them. The way we conceptualize pain depends largely on the nature of the information acquired and the models that we were exposed to during our training. In the first section of this chapter, we review the historical models of how we conceptualized pain. We will argue that although these models are not necessarily inaccurate, they are incomplete. We then suggest that a broader, multidimensional perspective is required to understand pain and to treat patients appropriately. We describe the role of behavioral, cognitive, and affective factors that have been shown to be relevant to the experience of pain, disability, and response to treatment. We provide data demonstrating that these psychological factors may have an effect both on patients’ behavior and physiology. Finally, we raise the issue of the “patient uniformity myth” and describe the subgroups of pain patients based on psychosocial and behavioral characteristics. We provide data suggesting that knowledge of such patient subgroups may serve as a basis for matching patients to treatments based on their characteristics.
UNIDIMENSIONAL SENSORY “SOMATOGENIC” MODEL
Historically, pain has been understood from the perspective of Cartesian dualism in which pain was viewed as purely sensory, reflecting the degrees of incoming noxious sensory stimuli. This perspective assumes that there are two ends to a pain pathway. At the periphery, there are sensory receptors (nociceptors), where noxious information is received and, at the other end, regions located in the brain where information is registered passively. From this perspective, noxious stimulation inevitably results in the sensation of pain, as if pulling a string at the periphery activates a bell located in the brain. Variations of this model have been prominent since first proposed by Descartes in 1644.
A central belief of sensory models is that the amount of pain experienced is a direct result of the amount, degree, or nature of sensory input or physical damage and is explained in terms of specific neuro physiological ...