Over the past four decades, approaches to the assessment of chronic pain have evolved substantially within the field of behavioural medicine. During this time, it has become apparent that what we label as ‘pain’ is the result of complex interactions among biological, psychological and social factors. The gate control theory of pain (Melzack & Wall, 1965) supports this paradigm in that it confirms that pain is a complex experience involving sensory–discriminative, evaluative–cognitive and affective–motivational components, thus emphasizing the role of the central nervous system in nociceptive perception and processing. Further, the gate control theory provides a foundation for the development and refinement of integrated pain assessment models, such as the biopsychosocial model of pain (Turk, 1996).
The biopsychosocial model of pain acknowledges that the experience of pain often is the result of physiological changes occurring after peripheral nociceptive stimulation (Turk, 1996). However, this model also emphasizes that the pain experience is modulated by individual differences in various cognitive, affective, behavioural and social factors. People with the same level of underlying nociceptive stimulation may differ in their pain experience depending on the importance of any factor at any given time during the course of the disease or condition (Asmundson & Wright, 2004). Thus, assessing pain necessitates the examination of relations among various factors across a variety of levels (Stoney & Lentino, 2000).
During the latter part of the twentieth century, Melzack (1999) proposed an expanded model of pain which further highlights the role of psychological processes in pain.