Objectives: Pain is a common symptom with high occurrence in somatoform syndromes and depressive disorders. Research in this area often focuses on experimental induction of pain and subsequent assessment of pain thresholds, ensuring repeatable stimuli of defined quality. Results on sensitivity to experimental pain in major depression are inconclusive, and data on pain thresholds in multiple somatoform symptoms are scarce. The goals of the present study were to differentiate between groups regarding the pressure pain thresholds, and to investigate the possible influence of physical activity on the pain thresholds in these groups. We postulate that physical fitness and physical activity influence pain thresholds in depression and persons with multiple somatoform symptoms.
Methods: Thirty-eight persons with major depression, 26 persons with a minimum of 6 to 8 somatoform symptoms (somatoform symptom index 8, SSI-8), and 47 healthy participants participated in the study. Baseline values of pressure pain thresholds assessed at different sites of the body were compared with those after 1 week of increased and 1 week of reduced physical activity.
Results: We used repeated measurement design (MANCOVA) and partial correlations for data analysis. Depressed participants reported lower pain thresholds compared with controls, and persons with SSI-8 showed intermediate thresholds. After 1 week of physical activity, participants reported higher pain thresholds. Men had higher pain thresholds following activity as compared with women. Participants who reported higher general fitness also showed higher pain thresholds. Sensitivity to pressure pain is associated with depression, but not with multiple somatoform symptoms.
Discussion: Short low-graded exercise can have reducing effects on perception of pressure pain. Physical activity level is a relevant covariate when using pressure pain assessment. Reduced general fitness can partially account for lower pain thresholds in depression.