Alpha-band fronto-limbic hyperconnectivity in adolescents with major depression and suicidal ideation.

BACKGROUND: Adolescents with major depressive disorder (MDD) are at high risk for suicide, but the neurophysiological correlates of suicidal ideation remain unclear. Resting-state EEG functional connectivity offers a promising approach to investigating brain network alterations associated with suicide risk. METHODS: We recruited first-episode, treatment-naïve adolescents with MDD with suicidal ideation (SI-MDD, n = 30), without suicidal ideation (NSI-MDD, n = 38), and healthy controls (HC, n = 33). Resting-state EEG was used to construct source-level functional connectivity networks based on the weighted phase lag index. Network-based statistics (NBS) identified between-group differences in subnetworks, and graph-theoretical analysis quantified global and nodal topological properties. Correlations with Hamilton Depression Rating Scale (HAMD) scores were examined. RESULTS: In the alpha band, NBS identified significantly enhanced functional connectivity in the SI-MDD group compared to the NSI-MDD group, comprising a subnetwork of 25 regions and 47 connections. This subnetwork formed a right-lateralized fronto-limbic circuit where all connections involved at least one frontal node. Key hubs with the highest node degrees included the right olfactory cortex, right superior medial frontal gyrus, and right middle orbital gyrus. Graph-theoretical analysis indicated that nodal efficiency decreased from HCs to NSI-MDD but recovered to near-normal levels in SI-MDD. Furthermore, exploratory analyses revealed that nodal properties were positively correlated with HAMD scores in the NSI-MDD group, but negatively correlated in the SI-MDD group. CONCLUSION: The observed right-lateralized frontal hyperconnectivity in the alpha band in this study provides critical clues for understanding the neural mechanisms underlying adolescent depression patients with SI and for targeted neuromodulation interventions.