Chronic pain and outcome in a pain clinic population: The relationship between etiology and psychological functioning.

Abstract

The SCL-90-R profiles of 83 intractable pain patients attending a southwestern university-affiliated medical center were analyzed with a clustering procedure. As hypothesized, this analysis resulted in three cluster groups: one cluster did not show any elevations on the clinical scales, a second cluster displayed high scores on the somatization and depression scales, while the third cluster endorsed elevations on the majority of the clinical scales. Contrary to the hypothesized prediction, there was no difference between the cluster groups and the three treatment outcome groups, although the lack of significant findings may be secondary to a weak treatment effect. There was also no difference between the cluster groups and the three pain etiology groups composed of neurogenic, musculoskeletal or both neurogenic and musculoskeletal patients. A discriminant function analysis performed on other psychological variables including global severity, somatic anxiety, somatic depression, cognitive anxiety, cognitive depression, coping style, depression, and pain intensity as predictors of membership in the treatment outcome groups was not statistically significant, although this procedure correctly classified patients at a rate substantially higher than chance. On the majority of the above psychological variables, patients with the best treatment outcome showed lower levels of distress, while patients in the poor outcome group displayed higher degrees of distress. A similar discriminant function analysis with the eight psychological variables as predictors of the three pain etiology groups also provided no statistically significant results. Finally, among several demographic and clinical variables only the length of illness and number of medications utilized significantly discriminated the three outcome groups. The implications of this study and suggestions for future studies in the pain management field are provided.