Bridging the gap between poles: Network structure and bridging mechanisms of depressive and hypomanic symptoms in a large-scale psychiatric outpatient sample.

BACKGROUND: The co-occurrence of depressive and hypomanic symptoms complicates mood disorder assessment and treatment. However, the symptom pathways linking these domains remain poorly understood. This study examined the network structure of depressive and hypomanic symptoms to identify key bridge symptoms. METHODS: Cross-sectional data from 6913 psychiatric outpatients were analyzed using the Beck Depression Inventory-II (BDI-II) and Hypomania Checklist-32 (HCL-32). A Gaussian Graphical Model estimated symptom associations, and bridge centrality indices identified symptoms linking depressive and hypomanic communities. A Network Comparison Test evaluated differences between a Depressive Symptoms (DS) group and a Hypomanic-like Symptoms (HyS) group. RESULTS: Two distinct but interconnected symptom communities were identified. Irritability (HCL26), suicidal thoughts (BDI-II9), and impatience (HCL25) showed the highest bridge strength, indicating strong cross-domain connectivity. Social activity (HCL15) and loss of interest (BDI-II12) had the highest bridge betweenness, suggesting important roles in linking behavioral activation and depressive symptoms. Although overall network structure did not differ significantly between groups, the DS group showed higher global strength, indicating stronger overall symptom interdependence. CONCLUSIONS: Irritability, social over-activation, and related symptoms occupy central positions connecting depressive and hypomanic symptom communities. These bridge symptoms may represent transdiagnostic indicators of affective symptom connectivity and provide potential directions for future longitudinal studies examining symptom evolution and clinical relevance.