The dimensions of pain: a multidimensional scaling comparison of cancer patients and healthy volunteers.

This paper presents a new approach to the measurement and understanding of clinical pain. A multidimensional scaling (MDS) procedure was used to analyze pairwise similarity judgments made to 9 pain descriptors by 24 cancer pain patients and 24 healthy volunteers. The question was whether the dimensions of the global pain space differed between the 2 groups. The Pain Intensity dimension was found to be primary for the patients, but much less important for the volunteers. Otherwise, the group stimulus space revealed broadly similar 3-dimensional solutions. The Pain Intensity dimension placed Mild Pain and Annoying at one pole and Intense and Unbearable Pain at the other. The Emotional Quality dimension grouped the descriptors Sickening and Miserable (and, in part, Intense Pain and Unbearable Pain) at the strong negative affect pole for both groups; they differed, however, with respect to the moderate affect pole. The Somatosensory dimension ranged from Burning to Cramping. The subject weight space revealed that the Pain Intensity dimension was the most important dimension for the patients, while Emotional Quality was more salient for the volunteers. Wide differences were found in the salience of the various dimensions to different individuals; this information may prove useful for tailoring patient treatment. The study demonstrates that MDS procedures such as INDSCAL, in which the subjects (rather than the researcher) determine the number and characteristics of the global pain dimensions, will improve our understanding and treatment of pain.