Re-conceptualizing sensitization in pain: A case for a behavioural approach

Sensitization refers to the increase in behavioural response to a repeated stimulus. The International Association for the Study of Pain (IASP) conceptualizes sensitization from a neural perspective and defines it as an increased responsiveness of nociceptive neurons. However, labelling behavioural changes and potential explanatory mechanisms with the same term causes a great deal of confusion and should therefore be avoided. We propose a behavioural approach for the study of sensitization. We suggest not to label sensitization as a mechanism but as the behavioural outcome (effect) of a procedure and propose to operationally define sensitization as a behavioural response increment that results from repeated exposure to the same stimulus. New and carefully-designed behavioural studies that aim to investigate the effect of state- and contextual factors on pain sensitization are expected to provide better understanding of why some people show more sensitization to pain then others.