Altered EEG microstate associated with anxiety and somatization symptoms in major depressive disorder.

Objective: To examine abnormalities in EEG microstate dynamics in patients with major depressive disorder (MDD) and to explore their associations with anxiety and somatization symptoms. Methods: We enrolled 30 patients with MDD and 40 healthy controls. Resting-state EEG was recorded and analyzed using microstate segmentation (classes A-D). Temporal parameters (mean duration, occurrence, time coverage, and transition probabilities) were compared between groups, and correlations with clinical symptoms (HAMD, HAMA, MADRS) were examined. Results: Compared with controls, patients with MDD exhibited a significantly longer duration, higher occurrence, and greater time coverage of microstate C, while microstate B showed reduced occurrence and coverage. Transition probability analyses revealed fewer transitions from A to B, A to D, B to A, B to D, and D to A, and more transitions between C and D. Symptom correlations indicated that microstate B occurrence was positively associated with HAMD anxiety/somatization scores, while transitions from C to D and from D to C were negatively correlated with anxiety/somatization scores. Conclusions: MDD is characterized by alterations in microstate B and C dynamics and disrupted transitions between C and D, some of which relate to symptom dimensions, suggesting that EEG microstate features may serve as potential neurophysiological markers in major depressive disorder.