To explore the causal relationship between academic procrastination, negative emotions, self-control, and smartphone addiction among college students, so as to provide theoretical reference for promoting their mental health and academic achievement.

A multi-stage cluster random sampling method was used to select 452 first-year students from a university in Guangzhou as the research subjects. Procrastination Assessment Scale- Student (PASS), The Depression Anxiety Stress Scale (DASS-21), Self Control Scale, and Short Version of the Smartphone Addiction Scale (SAS-SV) were used as measurement tools. Three questionnaire surveys were completed in October 2024 (T1), February 2025 (T2), and May 2025 (T3). Coss-lagged models were utilized to analyze the causal relationship between academic procrastination, negative emotions, self-control, and smartphone addiction.

The SAS-SV scale for college students showed an average score of (40.52±1.96), with 43.1% of freshmen exhibiting smartphone addiction.Positive correlations were observed between academic procrastination, negative emotions, and smartphone addiction across different time points, while self-control exhibited negative correlations with these three variables (r=0.30-0.62, -0.72 to -0.34, all P < 0.05). Cross-lagged model results indicated that academic procrastination and negative emotions at T1 and T2 positively predicted smartphone addiction at T2 and T3 (T1→T2, β=0.22, 0.35; T2→T3, β=0.21, 0.24; all P < 0.05). Self-control negatively predicted smartphone addiction (T1→T2, β=-0.32; T2→T3, β=-0.26; both P < 0.05). In reverse-causality regression models, smartphone addiction at T1 and T2 positively predicted academic procrastination and negative emotions at T2 and T3 (T1→T2, β=0.09, 0.24; T2→T3, β=0.10, 0.35; all P < 0.05), but no statistically significant predictions were found for self-control (T1→T2, β=-0.04; T2→T3, β=-0.03; both P>0.05).

Academic procrastination and negative emotions exhibit bidirectional causality with smartphone addiction among college students, while self-control unidirectionally predicts smartphone addiction.