Impact of depression on experimental pain perception: A systematic review of the literature with meta-analysis

Objective: This systematic review and meta-analysis was performed to examine the impact of depression on the perception of experimental pain stimuli. Methods: CD-ROM databases and bibliographies were searched to identify studies comparing the psychophysical responses to experimental pain stimuli of depressed subjects with that of healthy controls. Effect sizes (Cohen's d) and probabilities were combined across studies; positive effect sizes indicated higher thresholds in depressed groups. Results: Six methodologically rigorous, independent studies were found comparing psychophysical responses to experimental pain stimuli in depressed subjects and healthy controls. Pain perception threshold was higher in depressed subjects (6 studies, d = 0.38, p = .001). This finding was not the result of publication bias. Absolute sensory perception threshold was much higher in depressed subjects (2 studies, d = 0.68, p = .002), though the findings for pain tolerance (2 studies) were too heterogeneous to enable us to combine results. Conclusions: Depressed subjects are less likely to perceive a sensory stimulus as being painful compared with nondepressed controls. The influence of depression on attention to the pain stimulus may account for this effect. More studies are required to enable us to determine the impact of depression on absolute sensory perception threshold and pain tolerance. Furthermore, more studies would enable the examination of depression on the perception of different modalities.