Objective: To examine the associations of pet ownership and daily outdoor activity duration with depressive symptoms in middle school students, so as to provide evidence for targeted prevention strategies of depressive symptoms in middle school students. Methods: Using a stratified cluster random sampling method, 83 601 middle and high school students from 103 districts and counties in Inner Mongolia Autonomous Region were selected in 2024. A questionnaire survey was conducted to collect demographic data, household pet ownership, outdoor activity duration, and depressive symptoms of the research subjects. The comparison of reporting rates of depressive symptoms among different groups of middle school students was conducted using a χ 2 test. The association between pet ownership and outdoor activity duration and depressive symptoms among middle school students was evaluated using a Logistic regression model, and stratified analysis was conducted among different genders and regions to control for potential confounding factors and evaluate the stability of the association. Results: The prevalence of depressive symptoms among middleschool students in Inner Mongolia was 17.2%. Significant differences in depressive symptom reporting rates were observed across sex, grade, ethnicity, surveillance site, parental education, menarche/spermarche status, boarding status, smoking and alcohol use, daily breakfast consumption, school bullying, continuous 30 minute headphone use in a noisy environment, and often use the Internet ( χ 2=8.07-2 672.57, all P <0.01). Both pet ownership ( OR =0.78, 95% CI =0.75-0.81) and ≥2 h/d of outdoor activity( OR =0.81, 95% CI =0.78-0.84) were inversely associated with depressive symptoms;compared to the without owning pets and < 2 h of outdoor activity daily group, students who both owned pets and engaged in ≥2 h of outdoor activity daily had an even lower risk ( OR =0.83, 95% CI =0.78-0.87)(all P <0.05). Conclusion Pet ownership and increased daily outdoor activity duration may help mitigate depressive symptoms among middle school students.

Objective: To explore the bidirectional associations among body mass index Z scores (BMI Z scores) and weight stigma with depressive symptoms in adolescents, thereby providing evidence for targeted intervention strategies. Methods: A stratified cluster random sampling method was employed to select 18 301 adolescents aged 12-18 years from all 12 prefectures (103 counties) in the Inner Mongolia Autonomous Region, and two waves of longitudinal surveys were conducted in September 2023 (T1) and September 2024 (T2) among the adolescents. Weight stigma was assessed by using a self developed questionnaire, depressive symptom was measured with the Center for Epidemiologic Studies Depression Scale (CES-D), and BMI Z scores were calculated according to the World Health Organization standards. Pearson correlation analysis was used to examine associations among variables, and cross lagged panel models were constructed to investigate the dynamic bidirectional relationships among the three variables. Results: Adolescents BMI Z scores and weight stigma with depressive symptoms all exhibited autoregressive stability across the two time points (autoregressive paths, all P <0.01). Cross lagged model comparisons indicated that the bidirectional path model achieved the best fit ( χ 2=12.65, RMSEA =0.017, CFI =1.000; △ χ 2=193.39, P <0.01), supporting dynamic bidirectional associations among the three variables. After adjusting for gender, age, subjective social status and only child status, T1 BMI Z scores among adolescents positively predicted T2 weight stigma ( β =0.061), and T1 weight stigma positively predicted T2 depressive symptoms ( β =0.608); in the reverse direction, T1 depressive symptoms predicted T2 weight stigma ( β =0.003), and T1 weight stigma predicted T2 BMI Z scores ( β =0.081) (all P <0.01). Conclusions There is a bidirectional cross lagged relationship among adolescents BMI Z scores and weight stigma with depressive symptoms, suggesting that weight stigma may serve as a key psychological variable linking obesity and depressive symptoms. Greater attention should be paid to the potential threat of weight stigma to adolescents mental health, with intervention strategies expanded from a solely physiological focus to encompass psychosocial dimensions.

Objective: To investigate the changing trends for associations of anxiety and depressive symptoms with smartphone addiction among middle school students, so as to provide a scientific basis for preventing smartphone addiction in middle school students. Methods: From 2022 to 2023, a method of combining convenient sampling with cluster sampling was used to select 8 923 middle school students from 27 junior high schools and 3 senior high schools in a district of Shenzhen City between September 2022 (baseline, T1) and September 2023 (follow up, T2). The Smartphone Addiction Scale-Short Version (SAS-SV), Patients Health Questionnaire-9 Item (PHQ-9), and Generalized Anxiety Disorder 7-item Scale (GAD-7) were administered to assess smartphone addiction, anxiety and depressive symptoms. Mixed effects models were used to analyze the association of anxiety and depressive symptoms with smartphone addiction among middle school students. Results: From September 2022 to September 2023, the reported prevalence of smartphone addiction increased from 24.22% to 25.25% ( χ 2=45.71); and smartphone addiction scores [ 24.00 (16.00, 32.00),25.00(16.00, 33.00)], anxiety symptom scores [2.00(0.00, 7.00),3.00(0.00, 7.00)] and depressive symptom scores[3.00(0.00, 8.00),5.00(0.00, 9.00)] all significantly increased ( Z =-17.43, -42.38, -41.57) (all P <0.05). There were statistically significant difference in the distribution of anxiety and depression symptom levels among middle school students in 2022 and 2023 ( χ 2=85.15, 106.85, both P <0.05). After adjusting for covariates such as age, gender and family background, mixed effects models revealed dose response associations of anxiety and depressive symptoms with smartphone addiction among middle school students:mild anxiety symptom( OR =3.22), moderate to severe anxiety symptom ( OR =5.36), mild depressive symptom ( OR =3.32) and moderate to severe depressive symptom ( OR =6.13) were significantly associated with higher risks of smartphone addiction (all P <0.05). Interaction effect analysis found that co existing anxiety and depressive symptoms synergistically increased addiction risk by 5.60 times ( OR =5.60) compared to the asymptomatic group, with 32% of the combined risk attributable to their interaction ( S=1.64, AP =0.32)(both P < 0.05 ). Conclusions Anxiety and depressive symptoms are significantly associated with smartphone addiction, exhibiting a synergistic effect. Attention should be paid to emotional issues and smartphone addiction among middle school students.

Objective: To analyze the prevalence trends of different types of elevated blood pressure and their association with nutritional status among primary and secondary school students in Inner Mongolia from 2019 to 2024, providing references for targeted prevention strategies. Methods: From September 2019 to 2024, a stratified random cluster sampling method was used to select 12 primary and secondary schools from each league city in Inner Mongolia Autonomous Region. A total of 177 108, 137 758, 190 182, 180 084 , 188 056, 180 351 primary and secondary school students (excluding grades one to three of primary school) were included for physical examination. The correlation between their nutritional status and high blood pressure was analyzed based on the basic situation of 129 821 primary and secondary school students who completed a questionnaire survey at the same time in 2024. Statistical analysis was conducted using a Chi-square test and multiple Logistic regression model. Results: From 2019 to 2024, the detection rates of elevated blood pressure were 13.60%, 13.68%, 17.60%, 17.24%, 14.77% and 15.96%, respectively. The rates for isolated systolic hypertension were 4.24%, 5.83%, 7.26%, 7.19%, 6.24% and 6.93%; isolated diastolic hypertension rates were 6.38%, 4.99%, 6.23 %, 6.41%, 5.39% and 5.66%; and combined systolic and diastolic hypertension rates were 2.97%, 2.86%, 4.11%, 3.65%, 3.14 % and 3.36%. Multivariate Logistic regression analysis showed that girls, junior high school, senior high school, overweight, and obesity were positively associated with elevated blood pressure risk ( OR =1.27, 1.25, 1.32, 1.66, 3.07, all P <0.05); conversely, county residence, Mongolian ethnicity, and other ethnicities showed negative associations ( OR =0.90, 0.93, 0.90, all P <0.05). Conclusions Overweight and obesity among children and adolescents are closely related to various types of elevated blood pressure. Prevention strategies should prioritize effectively controlling weight issues among children and adolescents, thereby effectively reducing the incidence of elevated blood pressure.

Objective: To explore the association between negative life events and smartphone addiction among middle school students, so as to provide theoretical support and practical guidance for prevention and intervention of smartphone addiction among middle school students. Methods: Using cluster sampling, 8 890 students were selected to survey from 27 junior high schools and 3 senior high schools in a district of Shenzhen in 2022 (baseline) and 2023 (followup). Data were collected through selfresigned questionnaires on basic information, the Smartphone Addiction Scale-Short Version, and the Adolescent Selfrating Life Events Checklist. Mixedeffects models were employed to analyze the association. Results: Compared to 2022, the punishment scores of middle school students in 2023 [1.00 (0.00, 6.00) and 1.00 (0.00, 6.00)] decreased (Z=4.27), while the scores of interpersonal stress, learning stress and adaptation [4.00(0.00, 8.00), 4.00(0.00, 8.00); 4.00(1.00, 8.00), 5.00(2.00, 9.00); 2.00 (0.00, 6.00), 3.00 (0.00, 7.00)] increased (Z=-3.04, -8.36, -6.80) (P<0.01). Mixedeffects models revealed a positive doseresponse relationship between negative life events and smartphone addiction (OR=1.08-1.17, P<0.01). Stepwise regression showed independent positive effects of interpersonal stress (OR=1.05), academic stress (OR=1.03), and adaptation stress (OR=1.11) on smartphone addiction (P<0.01). Subgroup analysis of nonaddicted students in 2022 confirmed persistent associations for academic stress (OR=1.03) and adaptation (OR=1.07) (P<0.01). Conclusion Negative life events exhibit a positive doseresponse relationship with smartphone addiction, particularly interpersonal stress, academic stress, and adaptationrelated events.

Objective: To explore the longitudinal association between only-child status and smartphone addiction among middle school students, so as to provide a basis for establishing family intervention measures for smartphone addiction in middle school students. Methods: In October 2022 and October 2023, a preliminary survey and follow-up were conducted among 8 759 middle and high school students from 30 schools in a district of Shenzhen. A self-designed questionnaire was used to determine whether the students were the only-child, and the Chinese Version of the Smartphone Addiction Scale-Short Version (C-SAS-SV) was utilized to assess the students smartphone addiction status. A multilevel mixed-effects model and subgroup analysis were applied to examine the association between only-child status and smartphone addiction among middle school students. Results: During 2022 to 2023, the prevalence of smartphone addiction in the cohort of middle school students increased from 24.1% to 25.2%. Compared with only-child, non-only child were more likely to be addicted to smartphones (adjusted model: OR =1.2, 95% CI =1.1-1.4) and also scored higher on smartphone addiction (adjusted model: β =0.9, 95% CI =0.2-1.5)( P <0.05). Subgroup analysis further revealed that compared to baseline, non-only child demonstrated an increased prevalence of smartphone addiction (adjusted model: OR = 1.2 , 95% CI =1.0-1.5) and higher addiction scores (adjusted model: β =0.8, 95% CI =0.2-1.5) after one year( P <0.05). Conclusions Non-only child face higher risk of smartphone addiction. Under the current population policy, it is crucial to address smartphone addiction among middle school students who is not only child.

Objective: To explore the potential causal association between adolescent compulsive behaviour and smartphone addiction based on longitudinal data, so as to provide reference for the establishment of adolescent smartphone addiction interventions. Methods: A preliminary survey and follow-up were conducted on 8 907 middle and high school students in a district of Shenzhen in 2022 and 2023, respectively. Compulsive behaviours were measured by using the Mental Health Inventory for Middle School Students-60 Items (MMHI-60), smartphone addiction was assessed by using the Smartphone Addiction Scale-Short Version ( SAS- SV), and the associations between compulsive behaviours and smartphone addiction were analysed by using multilevel mixed-effects models and subgroup analyses. Results: Smartphone addiction detection rates among middle school students were significantly associated with genders, father s education level, mother s education level, study load subgroups, and whether or not they were single-parent families, and there were statistical differences ( χ 2=17.21-175.34, P <0.05). Students with compulsive behaviours were 2.98 times more likely to develop smartphone addiction than those without compulsive behaviours ( OR=2.98, 95%CI=2.77-3.22, P <0.05). Subgroup analysis of middle school students without smartphone addiction in the first year found that compulsive behaviours significantly predicted smartphone addiction ( OR= 1.76 , 95%CI=1.54-2.01, P <0.05). Conclusion There is a potential causal association between obsessive-compulsive behaviours and smartphone addiction in middle school students, and obsessive-compulsive behaviours in middle school students could significantly predicted the occurrence of smartphone addiction.

Objective: To analyse associated factors of campus bullying in schools, and to construct a nomogram model to predict the risk of campus bullying, so as to provide a theoretical basis for campus bullying prevention and control. Methods: In September 2023, 89 117 middle and high school students were selected by stratified cluster random sampling method within 12 cities (103 counties) in Inner Mongolia, and were surveyed with self administered questionnaire. Among them, there were 62 381 participants in the training set and 26 736 participants in the testing set. Statistical analysis was conducted using χ 2 test and multiple Logistic regression, and a nomogram model was drawn for predicting campus bullying. Results: The prevalence of campus bullying was 3.49%. Living in a suburban county, living in an unstable family, not the only child, having a father with a college degree or above, sometimes or never eating breakfast, being overweight or obese, living on campus, being scolded by parents in the past 30 days, smoking, Internet addiction, experiencing depression, anxiety symptoms, recreational soluble solvents use, cough medicine abuse, nonprescribed use of sedatives were all positively correlated with campus bullying ( OR =1.18, 1.40, 1.12, 1.33, 1.13, 1.72 , 1.12, 1.17, 1.82, 1.32, 1.83, 3.92, 2.40, 2.25, 1.51, 1.63, P <0.01).There were a negative correlation between high school students, female students, and the number of physical education classes per week (2-3, ≥4) with campus bullying ( OR =0.67, 0.58, 0.72, 0.83, P <0.01). The prediction model of campus bullying risk was established by nomogram model. The area under curve (AUC) was 0.82, and the calibration curve showed that the predicted value was close to the actual value. Conclusions Bullying among middle and high school students are related to family intimacy, poor daily behaviour and psychological factors. Targets of bullying intervention in schools should be identified, and preventive and control measures against bullying in secondary schools should be formulated, so as to reduce the occurrence of campus bullying.

Objective: To understand smoking behavior and related factors among college and middle school students in Inner Mongolia Autonomous Region, so as to provide a technical basis for targeted tobacco control interventions. Methods: In September 2023, a total of 93 647 students in Inner Mongolia Autonomous Region were randomly selected by stratified cluster sampling from 12 league cities and 103 banner counties (cities districts) to conduct a questionnaire survey. The χ2 test and binary Logistic regression analyses were used to explore the current situation of adolescent smoking and its related factors. Results: The prevalence of college and middle school students who tried smoking was 10.2%, and the prevalence of current smokers was 4.4%. The binary Logistic regression model showed that students in high school, vocational high school, university, males, those from unstable family, boarders, individuals who sew someone smoking at home, at school, in public places, drinking alcohol, inhaling volatile solvents for pleasure, using cough suppressant except for coughing, using sedative without a doctors permission, being scolded by parents, experiencing school bullying, being addicted to the Internet, having depressive symptoms, anxiety symptoms, and low selfesteem were more likely to attempt smoking and currently smoke (attempt smoking:OR=1.38, 2.59, 1.75, 3.24, 1.18, 1.43, 1.25, 1.43, 1.43, 0.79, 9.18, 1.42, 1.17, 1.65, 1.52, 1.31, 1.58, 1.41, 1.11, 1.17； current smoking:OR=1.61, 4.76, 3.76, 4.45, 1.17, 1.44, 1.27, 1.58, 1.69, 0.68, 7.99, 1.64, 1.12, 2.31, 1.48, 1.37, 1.26, 1.31, 1.35, P<0.05). Teenagers with parents who had graduated from high school and eat breakfast every day had a relatively low risk of trying and current smoking (OR=0.78, 0.83, 0.79, 0.84, 0.78, 0.68, P<0.05). Conclusions Adolescent smoking behaviours in Inner Mongolia Autonomous Region exhibit obvious clustering pattern in the school setting. Associated factors includes demographic characteristics, secondhand smoke exposure, daily behaviours and substance abuse, and psychological behaviours. Schools, families and society should work together to create a smokefree environment to protect adolescents from the harms of tobacco.

Objective: To analyse the correlation between unhealthy lifestyles and anxiety symptoms among high school students in Inner Mongolia Region, so as to provide a scientific basis for the prevention of anxiety symptoms among high school students. Methods: From September to November 2023, 35 362 high school students were selected by stratified cluster random sampling method from 12 cities (103 counties) in Inner Mongolia Region, and the survey was conducted by using the questionnaire on student health status and influencing factors. The χ2 test and multivariate Logistic regression analyses were used to determine the influencing factors of anxiety symptoms. Results: The total number of students with anxiety symptoms was 2 747, and the detection rate of anxiety symptoms was 7.77%. The results of multivariate Logistic regression analyses showed that female students, father having higher education background, never eating breakfast, being overweight and obese, sleeping <8 h/d, being scolded by parents in the past 30 days, and depressive symptoms were positively correlated with the anxiety symptoms of the high school students (OR=1.31, 1.23, 1.53, 1.14, 1.22, 1.51,28.92); nonsmoking, having no alcohol consumption, no Internet addiction and no use of sedatives without doctors permission were all negatively correlated with anxiety symptoms of high school students (OR=0.84, 0.73, 0.57,0.40) (P<0.05). Conclusions Anxiety symptoms of high school students are closely related to unhealthy lifestyle. Measures should be taken to improve unhealthy lifestyle, so as to reduce the occurrence of anxiety symptoms in high school students.