Linking Social Anxiety to Depressive Symptoms in Adolescents: The Dual Mediating Roles of Perceived Social Support and Sleep Quality

OBJECTIVE: Social anxiety is a key risk factor for adolescent depression, yet its underlying mechanisms and subgroup differences remain unclear. This study explored the mediating roles of perceived social support and sleep quality in their link, and the moderating effects of visit type and gender. METHODS: A retrospective observational study enrolled 386 depressed adolescents (12-18 years; 231 outpatients, 155 inpatients) from Xiamen Xianyue Hospital. Social anxiety, depressive symptoms, perceived social support and sleep quality were assessed using the Social Anxiety Scale for Adolescents, Self-Rating Depression Scale, Multidimensional Scale of Perceived Social Support and Pittsburgh Sleep Quality Index, respectively. Pearson's correlation and Hayes' PROCESS macro (Model 6) were applied for mediation/moderation analyses, with sensitivity testing via the Montgomery-Åsberg Depression Rating Scale (MADRS). RESULTS: Inpatients and severe cases had higher Social Anxiety Scale for Adolescents (SAS-A), Zung Self-Rating Depression Scale (SDS) and Pittsburgh Sleep Quality Index (PSQI) and lower Multidimensional Scale of Perceived Social Support (MSPSS) scores (all p < 0.001); females had higher social anxiety (p = 0.003). Social anxiety correlated positively with depressive symptoms (r = 0.54, p < 0.001) and negatively with perceived social support (r = -0.49, p < 0.001). Mediation analysis showed a total effect of social anxiety on depressive symptoms (β = 0.304, p < 0.001), with direct effect (57.5%, β = 0.175) and total indirect effect (42.5%, β = 0.130). Key indirect pathways: 'social anxiety → sleep quality → depressive symptoms' (27.0%) and a serial mediation pathway via perceived social support and sleep quality (8.2%); perceived social support's single mediation was marginally non-significant (p = 0.118). Moderation analyses revealed stronger direct effects in inpatients (β = 0.342 vs. 0.097, p < 0.001) and stronger sleep quality effects in females (β = 1.125 vs. 0.619, p = 0.006). MADRS sensitivity analyses confirmed consistency (path coefficient deviations <1%). CONCLUSIONS: Social anxiety affects adolescent depressive symptoms directly and via sleep-related mediation, moderated by visit type and gender. Targeting social anxiety and sleep quality may optimise precision prevention/treatment for adolescent depression.