Major depressive disorder in fibromyalgia: novel insights from resting-state functional connectivity analysis.

Background: Fibromyalgia (FM) and major depressive disorder (MDD) frequently co-occur. This study investigated whether the differences in resting-state functional connectivity (rs-FC) of the emotion- and pain-related brain networks may differentiate FM patients with and without MDD and if these differences are associated with the severity of clinical symptoms, quality of life, recurrent depression, pain catastrophizing, and antidepressant use.

Methods: In this study, the authors recruited a sample of 37 females classified as FM with MDD (FM + MDD, n = 23) or FM without MDD (FM-only, n = 14) based on the International Neuropsychiatric Interview. The severity of depressive symptoms was measured using the Beck Depression Inventory-II (BDI-II).

Results: Age-adjusted rs-FC correlated significantly with BDI-II scores. FM + MDD patients showed increased rs-FC between the right ventral insula and left middle frontal gyrus (MFG) (χ²(1) = 5.54, P = 0.019, effect size [ES] = 0.87), and decreased rs-FC between the caudal hippocampus and middle cingulate cortex (χ²(1) = 6.65, P < 0.001, ES = 0.90). Increased rs-FC between the ventral insula and MFG was positively associated with recurrent MDD and pain catastrophizing, and negatively with FM-related quality of life. The connection between the left MFG and the right posterior parietal thalamus is associated with recurrent MDD and pain catastrophizing.

Conclusions: Distinct neurofunctional patterns in regions related to emotional regulation and cognitive control of pain-marked by increased inter-hemispheric frontal and decreased intra-hemispheric limbic-cingulate connectivity-may serve as potential biomarkers to distinguish FM patients with comorbid MDD from those without.