Depression and the mediation of chronic pain

To explore Ward and colleagues' 1982 hypothesis of a biochemical link between depression and pain mediated by the paleospinothalamic tract (PSTT), the author retrospectively examined a series of questionnaires completed by 113 chronic pain patients. The measures included the Beck Depression Inventory, the Minnesota Multiphasic Personality Inventory, the Millon Behavioral Health Inventory, and a background questionnaire assessing demographic and pain variables that included portions of the McGill Pain Questionnaire (MPQ). Adjectives on the sensory scale of the MPQ were divided into two groups: those descriptive of pain mediated by the PSTT and those descriptive of pain mediated by the neospinothalamic tract (NSTT). To facilitate analysis of the data, two median splits were performed on the basis of PSTT and NSTT adjective scores to create four groups. Group differences were then examined by way of multivariate analysis of variance and chi-square. As hypothesized, psychologic distress was found to be related to the use of PSTT sensory adjectives but not to the use of NSTT sensory adjectives. The findings may be supportive of Ward et al.