Perceived stress and depression in Chinese university students: a parallel mediation analysis examining the roles of insomnia and somatic symptoms

Background: Previous studies have demonstrated the association between perceived stress and depression. A key question remains unclear whether insomnia and somatic symptoms function as simple manifestations of depression or serve as mediating roles in the stress-depression relationship, particularly among university students. This study explored how insomnia and somatic symptoms mediate the relationship between perceived stress and depression among university students in China. Methods: A total of 2,596 Chinese university students (68.3% female, mean age 22.3 ± 4.3) were included. The Perceived Stress Scale-10 (PSS-10), Insomnia Severity Index (ISI), Somatic Symptom Scale-8 (SSS-8), and Patient Health Questionnaire-9 (PHQ-9) were used to assess levels of perceived stress, insomnia, somatic symptoms and depression, respectively. Parallel mediation analysis revealed that perceived stress exerted both a direct effect [effect size = 0.382, 95% CI (0.357, 0.407)], and indirect effects [effect size = 0.235, 95% CI (0.214, 0.254)] on depression. The indirect effects, accounting for 38.1% of the total effect, were comparably mediated through insomnia (17.3%) and somatic symptoms (20.8%). Conclusion: In this cross-sectional study, insomnia and somatic symptoms served as significant parallel mediators in the association between perceived stress and depression among university students. These findings support the potential value of including interventions targeting sleep problems and somatic symptoms in depression prevention efforts for university populations.