Shared neurobiological changes in individuals with Crohn's disease and major depressive disorder

Emerging evidence highlights the profound impact of the central nervous system on the gut. This is particularly evident in inflammatory bowel disease, where psychological stress has been shown to modulate the inflammatory response and precede disease flares. The neuropsychological correlates of the brain's involvement in Crohn's disease (CD), as well as its overlapping neurobiological pathways with major depressive disorder (MDD), remain poorly defined. This study aims to delineate these shared mechanisms using ultra-high-field neuroimaging.

Resting-state functional magnetic resonance imaging was conducted on 13 CD patients (age range: 20-41 years; 9 males), 13 age-matched MDD patients (20-42 years; 9 males), and 13 healthy controls (HC) (19-42 years; 9 males) using a 7 Tesla MR scanner. Assessments for symptom severity included the Beck Depression Inventory-II (BDI-II) for depression and the Gastrointestinal Symptom Rating Scale (GSRS) for CD.

Significant differences in BDI-II scores are observed among the groups (χ² = 37.16, p < 0.0001), with CD patients scoring higher than HCs but lower than MDD patients. Correlation shows a positive association between GSRS and BDI-II scores in CD patients. Group-level fMRI analysis of normalized fALFF maps reveals significant clusters in the precuneus cortex. Subsequent seed-based connectivity analysis using the precuneus as seed region shows increased connectivity with the left supramarginal gyrus and decreased connectivity with the precuneus and anterior cingulate gyrus in MDD and CD compared to HCs.

These exploratory findings reveal similar abnormalities in brain activity and connectivity in CD and MDD. A deeper understanding of these interactions may enable integrated treatment approaches that address both psychological and physiological aspects of these interconnected conditions.