Convergent syndromic atrophy of pain and emotional systems in patients with irritable bowel syndrome and depressive symptoms

Irritable bowel syndrome (IBS) is a brain-gut disorder that is often accompanied by psychiatric comorbidities, particularly depression. However, the neuroanatomical substrates of IBS with depressive symptoms (DEP-IBS) and how depressive symptoms and brain morphology modulate IBS symptoms remain unknown. In this study, structural MRI data were processed using a voxel-based morphometry technique and one-way analysis of covariance (ANCOVA) and post-hoc t-tests were performed to compare gray matter volume (GMV) among 28 patients with DEP-IBS, 21 patients with IBS who lacked depressive symptoms (nDEP-IBS), and 36 healthy controls (HC). Correlation and mediation analyses were performed to evaluate the relationship between differing GMV in DEP-IBS and clinical variables. We found that GMV in the bilateral prefrontal, insular, and dorsal striatal areas, as well as the left temporal pole, were significantly lower in the DEP-IBS group than in the HC group. Moreover, compared with the nDEP-IBS group, the DEP-IBS group exhibited decreased GMV in the bilateral medial, dorsolateral prefrontal, and orbitofrontal cortices, bilateral dorsal striatum, and left insular cortices. Correlation analysis revealed that GMV in these atrophic brain areas of the DEP-IBS group was negatively correlated with depression, gastrointestinal symptoms, and disease duration. Our results further revealed that depressive symptoms served as a mediator between gastrointestinal symptoms and GMV in the left insula, right medial prefrontal cortex, and right middle frontal gyrus, while gastrointestinal symptoms served as a mediator between depression and GMV in these regions. Our results suggest convergent syndromic atrophy in the pain and emotional systems of patients with DEP-IBS.