The hidden burden: Sub-threshold mental symptoms, abnormal illness behavior, and their association with quality of life among college students

BACKGROUND: The high prevalence of mental disorders among college students underscores the importance of examining sub-threshold symptoms and their association with quality of life. OBJECTIVE: To investigate the association between sub-threshold symptoms and quality of life and to explore whether abnormal illness behavior mediates this relationship. METHODS: A cross-sectional study involving 7529 college students was conducted. Generalized linear models with linear regression analysis were used to examine the physical (PCS) and mental (MCS) component summaries of the 12-item Short-Form Health Survey (SF-12) in relation to anxiety, depression, somatization and insomnia symptoms. RESULTS: The prevalence of sub-threshold symptoms was 27.8 % for anxiety, 30.5 % for depression, 10.7 % for somatization, 10.8 % for insomnia, and 29.5 % for any comorbid pattern. Multivariate analysis revealed significant negative associations between sub-threshold mental symptoms and both PCS and MCS (P < 0.05). Median scores across all SF-12 dimensions were consistently lower in the sub-threshold group. Notably, abnormal illness behavior exhibited a negative mediating effect only in the above-threshold symptom group. CONCLUSION: Sub-threshold mental symptoms are highly prevalent among college students and are cross-sectionally associated with significant quality of life reduction. Specifically, our findings support a transdiagnostic intervention approach targeting stress load regulation-rather than symptom-specific interventions-as more clinically relevant for this population. Thus, colleges should prioritize stress-focused preventive strategies to mitigate symptom progression and functional impairment in sub-threshold students. Notably, abnormal illness behavior mediates the association between symptoms and quality of life only in the above-threshold group, indicating that colleges should tailor interventions differently for sub- versus above-threshold students.