Diffusion of pain language with affective disturbance confounds differential diagnosis.

Two experiments examined the use of pain descriptors by chronic pain patients with different medical and/or psychiatric diagnoses. Experiment I subjected patients' responses to the 20 descriptor categories on the McGill Pain Questionnaire to 3 separate multiple discriminant analyses to examine the differential diagnostic properties of pain language. None of the analyses generated a discriminant function, indicating that chronic pain patients do not use pain descriptors in a precise and systematic manner. Experiment II demonstrated that as affective disturbance increased within a chronic benign pain population pain language became more diffuse. These results suggest that pain language is not accurate for medical diagnosis in patients who suffer affective disturbance.