Selective Network Reweighting in Adolescents with Mood Disorders and Problematic Smartphone Use

Background and purpose Problematic smartphone use (PSU) is highly prevalent in mood-disordered adolescents, but it is unclear whether it reflects global disruption of functional architecture or specific circuits, and how it relates to depressive symptom. Methods A total of 199 adolescents with mood disorders (99 major depressive disorder, 100 bipolar disorder) were stratified into PSU (n = 86) and non-PSU (n = 113) groups using DSM-5–adapted criteria. Resting-state fMRI networks were analyzed with multi-scale graph measures across proportional densities. Hamilton Depression Rating Scale items were modelled as symptom networks to derive symptom communities and brain–symptom associations. Results Global small-world indices did not differ between groups. PSU was instead associated with selective reweighting at modular and nodal levels, including migration of attention regions into a hyper-cohesive reward–limbic core and reduced broadcast roles of executive hubs. Only in the PSU group did greater executive-network cohesion predict more severe anxiety-somatic symptoms. Conclusions In mood-disordered adolescents, PSU is instantiated as selective network reweighting, not global connectome breakdown, and alters the coupling between executive control and anxiety-somatic symptom clusters. These multi-level network signatures suggest mechanistic targets for interventions that rebalance communication among reward, salience and executive systems.