The chain mediation effect of self-regulation and pre-sleep smartphone use on the relationship between smartphone dependence and bedtime procrastination among college students.

Smartphone dependence and bedtime procrastination are prevalent behavioral issues among college students, yet the psychological mechanisms linking them remain underexplored. This study investigated the chain mediating roles of self-regulation and pre-sleep smartphone use in the relationship between smartphone dependence and bedtime procrastination. A sample of 1,482 Chinese college students completed validated measures of smartphone dependence, self-regulation, pre-sleep smartphone use, and bedtime procrastination. Structural equation modeling and bootstrap analyses (5,000 resamples) were employed, controlling for gender and academic year. Results revealed that smartphone dependence positively predicted bedtime procrastination (standardized total effect of 0.56; direct effect of 0.21, p < 0.001). Both self-regulation and pre-sleep smartphone use served as significant independent mediators. More importantly, the serial mediation pathway-smartphone dependence → self-regulation → pre-sleep smartphone use → bedtime procrastination-was also significant, with a total indirect effect; the aggregate total indirect effect across all three mediation pathways was 0.35. Critically, the serial indirect pathway-smartphone dependence → self-regulation → pre-sleep smartphone use → bedtime procrastination-was statistically significant with a modest standardized coefficient of 0.07. Robustness checks supported the stability of the model. Multi-group analyses further showed that the path from smartphone dependence to pre-sleep smartphone use was stronger among female students than among male students (β = 0.55 vs. β = 0.42), whereas the effects of smartphone dependence on self-regulation (β = -0.35 vs. β = -0.15) and pre-sleep smartphone use (β = 0.60 vs. β = 0.40) were stronger among lower-grade students than among higher-grade students. These findings clarify the multi-path behavioral mechanism from smartphone dependence to bedtime procrastination, highlighting self-regulation and pre-sleep smartphone use as critical intervention targets. Limitations include cross-sectional design and self-report data, warranting future longitudinal and objective assessments.