Abstract
Major Depressive Disorder (MDD) is a prevalent mental health condition, often accompanied by chronic pain. This study investigates the structural and functional characteristics of the thalamus in individuals with MDD, both with and without comorbid pain, using magnetic resonance imaging (MRI) techniques. A total of 165 participants, including healthy controls, individuals with MDD, and those with comorbid depression and pain, were enrolled. The study found a reduction of the left thalamus in the MDD group, while no significant differences in thalamic volume were observed in the right thalamus or in the depression and pain comorbidity group. Functionally, no significant differences in fractional amplitude of low-frequency fluctuations (fALFF) and regional homogeneity (ReHo) were found between groups. However, correlation analysis revealed associations between thalamic structure and cognitive performance, as well as clinical symptom severity in the depression and pain comorbidity group. These findings highlight the thalamus's role in the pathophysiology of MDD and its interaction with chronic pain, suggesting potential targets for diagnostic and therapeutic strategies.