Objective: To examine the dynamic relationship between campus bullying and loneliness among senior high school students, and the mediating role of school connectedness, in order to provide a basis to enhance adolescent mental health. Methods: In March 2023 (T1, baseline), a total of 880 first year senior high school students were recruited from 5 urban senior high schools in Xiangxi Tujia and Miao Autonomous Prefecture, Hunan Province, using the random cluster sampling method. The School Bullying Scale, School Connectedness Scale and UCLA Loneliness Scale were administered to assess the levels of school bullying, loneliness and school connectedness at T1 and follow up surveys [September 2023 (T2), March 2024 (T3)]. Mplus 8.3 software was used to construct cross lagged panel models and longitudinal mediation models to analyze the dynamic association between school bullying and loneliness among senior high school students, as well as the mediating effect of school connectedness in the relationship. Results: The scores of campus bullying among senior high school students at T1-T3 were (8.83±2.60)(8.57±2.42)(8.51±2.63), the scores of school connectedness were (32.51±6.40)(32.94±6.66)(29.22±6.78), and the scores of loneliness were (39.22±9.84)(38.67±9.97)(38.51±10.98). Pearson correlation analysis showed that campus bullying at T1-T3 was negatively correlated with school connectedness at T1-T3( r =-0.37 to -0.13) and was positively correlated with loneliness at T1-T3 ( r =0.19-0.43) among senior high school students, and loneliness at T1-T3 was negatively correlated with school connectedness at T1-T3 ( r =-0.53 to -0.29)(all P <0.01). Campus bullying at T1 positively predicted loneliness at T2 and T3( β =0.06, 0.25), whereas loneliness at T1 and T2 positively predicted respectively campus bullying at T2 and T3 ( β =0.09, 0.11)(all P <0.05). Campus bullying at T1 negatively predicted school connectedness at T2 ( β =-0.26), and school connectedness at T2 negatively predicted loneliness at T3 ( β =-0.14)(both P <0.05). School connectedness at T2 exerted a partial mediating effect between school bullying at T1 and loneliness at T3, and the mediating effect of school connectedness was 0.04 (95% CI =0.01-0.09). Conclusions Campus bullying and loneliness among senior high school students show a bidirectional predictive relationship. School connectedness plays a partial mediating role, suggesting that a strong school connectedness could help to mitigate the negative impact of campus bullying on adolescents loneliness.

Objective: To explore the association of latent profiles of mobile phone dependence and self control with physical exercise among junior high school students, so as to provide references for the prevention of mobile phone dependence and the improvement of self control among junior high school students. Methods: From April to May 2024, a stratified random cluster sampling method was used to select a total of 2 311 students from grade 7 to grade 9 in three public junior high schools in Xiangxi Autonomous Prefecture, Hunan Province. Latent profile analysis was conducted to identify the latent profiles of mobile phone dependence and self control among junior high school students. Pearson correlation analysis was used to examine the correlation between mobile phone dependence and self control, and Chi square test was used to analyze the distribution differences of latent profiles of adolescents across different demographic characteristics. Multiple Logistic regression analysis was applied to explore the association between mobile phone dependence, self control, and physical exercise. Results: Four latent profiles of mobile phone dependence and self control were identified: low dependence-moderate self control group ( n =885, 38.3%), moderate dependence-low self control group ( n =910, 39.4%), high dependence-no self control group ( n =232, 10.0%), and no dependence-high self control group ( n =284, 12.3%). Significant differences were observed in the distribution of latent profiles across gender, grade and only child status ( χ 2=10.85, 35.72, 13.85， P <0.05). Logistic regression analysis showed that, after controlling for demographic variables, compared with the low dependence-moderate self control group, physical exercise was negatively associated with the moderate dependence-low self control group ( OR =0.79) and the high dependence-no self control group ( OR =0.81), while positively associated with the no dependence-high self control group ( OR =1.58) ( P <0.01). Conclusions The influence of physical exercise on junior high school students different potential profile types of mobile phone dependence and self control is different. Schools and families should adopt targeted physical exercise interventions based on the characteristics of different profiles to promote the physical and mental health of junior high school students.