The impact of Smartphone addiction on depression symptoms among college students: the mediating role of bedtime procrastination and the moderating effect of psychological resilience

Objective To investigate the influence of Smartphone addiction on depression symptoms among college students, examine the mediating role of bedtime procrastination, and explore the moderating effect of psychological resilience. Methods Between October and December 2024, a stratified random cluster sampling method was employed to select 1,610 college students from four universities as research subjects. The Mobile Phone Addiction Index (MPAI), Bedtime Procrastination Scale (BPS), Patient Health Questionnaire-9 (PHQ-9), and Connor-Davidson Resilience Scale (CD-RISC-10) were used for data collection. Correlation analysis, mediation effect analysis, and moderated mediation model testing were conducted to analyze the relationships among variables. Results (1) Depression symptoms were significantly positively correlated with Smartphone addiction ( r = 0.456, p < 0.01) and bedtime procrastination ( r = 0.308, p < 0.01), and significantly negatively correlated with psychological resilience ( r = −0.331, p < 0.01). (2) Bedtime procrastination partially mediated the relationship between Smartphone addiction and depression symptoms, with an indirect effect of 0.284 (95% CI: 0.226~0.347), accounting for 19.08% of the total effect. (3) Psychological resilience significantly moderated the direct pathway between Smartphone addiction and depression symptoms (β=-0.017, p < 0.01), with individuals higher in psychological resilience demonstrating a weaker positive correlation between Smartphone addiction and depression symptoms. Simultaneously, psychological resilience significantly moderated the relationship between bedtime procrastination and depression levels (β = −0.004, p < 0.01), with a weaker positive correlation between bedtime procrastination and depression symptoms observed in individuals with higher levels of psychological resilience. Conclusion A moderated mediation model exists between Smartphone addiction and depression symptoms among college students, with bedtime procrastination serving as a partial mediator. Therefore, in preventing and intervening in depression symptoms among college students, attention should be paid to reducing excessive mobile phone use, improving sleep habits, and cultivating psychological resilience to enhance their ability to cope with challenges and stress, thereby effectively reducing the risk of depression symptoms.