Assessing pain in depression: what do ratings on unidimensional pain scales really mean?

Objective: The study aims to determine which dimensions of pain-somatosensory, affective, or evaluative-would predict unidimensional pain scores in patients with major depressive disorder (MDD); compare the results with findings in cancer and chronic musculoskeletal pain patients; and examine the relationship between pain complaints and psychopathology.

Methods: This is a 3-month prospective, observational study. Ninety-one Chinese patients were enrolled during an acute episode of MDD. Multidimensional Affect and Pain Survey (MAPS) was used to assess the multidimensional aspects of pain. Unidimensional pain intensity was evaluated using verbal rating scale (VRS) and visual analog scale (VAS). Hamilton Rating Scale for Depression and Hospital Anxiety and Depression Scale were used to assess depressive and anxiety symptoms.

Results: The VRS and VAS pain scores were more highly correlated with MAPS somatosensory supercluster than with Hamilton Rating Scale for Depression, Hospital Anxiety and Depression Scale, and MAPS emotional and well-being superclusters. Hierarchical regression analyses showed that unidimensional pain scores were predicted better by MAPS somatosensory than by emotional clusters. The explained variance of VRS and VAS scores could be improved by 9% to 16% by adding somatosensory clusters after controlling for emotional clusters, whereas 1% to 4% of the variance was improved by adding emotional clusters after controlling for somatosensory clusters. Pain intensity was more closely related to anxiety symptoms than to depressive symptoms cross-sectionally and longitudinally.

Conclusions: Our data suggest that pain and emotional symptoms in MDD are not entirely related. In cases in which pain symptoms are severe or remain persistent despite treatment of depression, specific strategy targeting pain may be needed.