The Deficit of Pain Inhibition in Fibromyalgia Is More Pronounced in Patients With Comorbid Depressive Symptoms

Abstract

BACKGROUND: On pathophysiologic grounds, fibromyalgia (FM) is characterized by a deficit in diffuse noxious inhibitory controls (DNIC), but the role of depressive symptoms on these mechanisms has not been investigated. We hypothesized that the deficit in pain inhibition would be more pronounced in FM patients with depressive symptoms (FM+D), relative to patients without such symptoms (FM-D). METHODS: Fifty-two women diagnosed with FM (American College of Rheumatology criteria) and 10 healthy women participated in this study. Thermal stimuli were used to measure pain thresholds and DNIC efficacy (spatial summation paradigm). Clinical pain was measured using visual analog scales. RESULTS: We found that the amplitude of DNIC was smaller in FM+D patients, relative to the FM-D group; and that daily pain (unpleasantness) was higher in the FM+D group, relative to FM-D patients. DISCUSSION: We found that FM+D patients have a more pronounced deficit in pain inhibition as well increased clinical pain. As such, these results show the usefulness of combining psychologic factors and psychophysical measures to identify subgroups of FM patients. These results may have implications for future treatment of FM patients with and without comorbid depressive symptoms.