Abstract Smartphones are a double edged sword, bringing convenience and access to new social resources for learning, social interaction, and entertainment, they also bring risks and problems such as smartphone addition, cybersecurity threats and cyberbullying. The study reviews the pros and cons of adolescent smartphone use and proposes the urgent need to enhance digital literacy. It suggests strengthening smartphone management across four levels—individual, family, school, and society, to provide comprehensive, multi layered support and guidance for adolescents in developing healthy smartphone usage habits.

Abstract The accelerated development of digital technology has brought new opportunities for the innovation of adolescent mental health service models. Through international case analysis, the paper finds that developed countries have established adolescent mental health service systems with significant digitalempowerment characteristics. For example, the Crisis Text Line of US realizes riskgraded responses by relying on language processing technology, the Kooth platform of UK develops an Artificial Intelligence (AI) counseling system using cognitivebehavioral therapy, ReachOut of Australia has established a digital mental health resource library, SPARX of New Zealand reshapes the treatment experience with a gamified interface, and "Annie Advisor" of Finland pioneers the application of affective computing technology. The above innovative practices present six characteristics: precision service supply based on big data, intervention systems integrated with artificial intelligence, anonymous mechanisms to ensure privacy and security, highly accessible services that break through time and space limitations, human-machine collaborative dual track support models, and interdisciplinary service systems, providing many references and implications for China to continuously and deeply explore digital technologyempowered youth mental health services.

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 analyze the heterogeneity of mobile phone dependence development trajectory in middle school students and its association with loneliness and selfcontrol ability, so as to provide reference for the prevention of mobile phone dependence in middle school students. Methods: A total of 941 grade 1 students from 4 public middle schools in Xiangxi Autonomous Prefecture, Hunan Province were selected for the followup survey by random cluster sampling from October 2023 to April 2024 and October 2024. Mobile Phone Addiction Index (MPAI), University of California, Los Angeles Loneliness Scale-20 (UCLA-20) and Selfcontrol Scales (SCS) were used for questionnaire survey. The heterogeneity of the developmental trajectory of middle school students mobile phone dependence was analyzed by the latent growth curve model (LGMM), and the influencing factors of the developmental trajectory of middle school students mobile phone dependence were explored by multiple Logistic regression analysis. Results: The development trajectory of middle school students mobile phone dependence could be divided into four categories: C1 "low risk slow decline group (n=438,44.6%)", C2 "medium risk slow rise group (n=272,29.7%)", C3 "high risk rapid decline group (n=73,8.6%)" and C4 "high risk rapid rise group (n=158,17.1%)". There were significant differences in the distribution of mobile phone dependence development track heterogeneity subgroups among sex, only child, lodging, and leftbehind students (χ2=117.79, 44.88, 37.09, 130.50, P <0.01). The results of the multinomial Logistic regression model analysis showed that, with C1 group as the reference, C2, C3, and C4 were positively correlated with students loneliness [OR(95%CI)=1.04 (1.02-1.06), 1.11(1.08-1.14), 1.12(1.09-1.14)]; C2 and C4 groups were negatively correlated with students selfcontrol [OR(95%CI)=0.97(0.96-0.99), 0.95(0.93-0.97)] (P<0.01). Conclusions The development trajectory of mobile phone dependence among middle school students is heterogeneous. Reducing the loneliness of individuals and cultivating good selfcontrol ability are helpful to alleviate mobile phone dependence behavior among middle school students.

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 relationship of physical exercise behavior with mobile phone addiction and mental health of college students, so as to provide evidence for interventions to improve mobile phone addiction and mental health of college students. Methods: From October 8 to December 20 in 2024, 896 college students from 4 colleges in Beijing were selected using a combination of convenience sampling and stratified random cluster sampling method. Physical Activity Rating Scale (PARS-3), Mobile Phone Addiction Tendency Scale (MPATS), Adolescence Mental Health Diathesis Questionnaire (AMHDQ) and Symptom Checklist 90 (SCL-90) were used. The correlation of mobile phone addiction and mental health on physical exercise behavior of college students were analyzed by multivariable Logistic regression and linear regression. Results: Among the surveyed college students, 504 (56.25%) students had low exercise, 262 (29.24%) had moderate exercise, 130 (14.51%) had high exercise, and 392 (43.75%) had sufficient exercise. The total score of PARS-3 was 18.00 ( 15.00 , 33.00) points. Logistic regression analysis showed that the total score of MPATS ( OR=1.022, 95%CI =1.008-1.036), the total score of SCL-90 ( OR=1.010, 95%CI = 1.005 -1.015), the total AMHDQ score ( OR=0.995, 95%CI =0.992-0.998) were significantly associated with insufficient exercise among college students ( P <0.05). Linear regression analysis showed that the scores of MPATS, AMHDQS and SCL-90 were significantly correlated with physical exercise behavior ( B=-0.20, 0.04, -0.07, P <0.05). Conclusion The physical exercise behavior of college students is related to mobile phone addiction and mental health.

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 analyze the association of eating dining locations and their association with nutritional status among Chinese children aged 6-17 years,so as to provide reference for guiding children s reasonable diet. Methods: Stratified random cluster sampling was used to select children aged 6 to 17 years from 28 cities and rural areas of 14 provinces in East, North, Central, South, Southwest, Northwest, Northeast of China, and a total of 52 535 children were included in the study from 2019 to 2021. Information including dining locations, demographic characteristics, dietary intakes and physical activity were collected through a questionnaire survey. Fasting body height and weight were measured in the morning. Unordered multiclass Logistic regression analysis was conducted to assess the relationship between dining locations and nutritional status in children. Results: Regarding children s dining locations, 66.3% ate breakfast at home,25.8% ate breakfast at school,7.9% ate breakfast outside (small dining tables, restaurants, stalls, etc.); 67.7% ate dinner at home,29.0% ate dinner at school,3.3% ate dinner outside; and 63.6% ate lunch at school,30.8% ate lunch at home,5.7% ate lunch outside. The prevalence rates of overweight/obesity and undernutrition were 28.6% and 9.3%, respectively. The adjusted multiclass Logistic regression analysis (controlling for age, region, parental education, household income, total energy intake, and moderate-to-vigorous physical activity) demonstrated that, compared to eating at home, school based breakfast and dinner consumption was associated with significantly lower overweight/obesity risks for both genders (boys: breakfast OR =0.70, 95% CI =0.65-0.75; dinner OR =0.80, 95% CI = 0.74- 0.86; girls: breakfast OR = 0.89 , 95% CI = 0.82-0.96; dinner OR =0.88, 95% CI =0.81-0.95), whereas eating lunch away from home significantly increased overweight/obesity risks (boys: OR =1.32, 95% CI =1.17-1.48; girls: OR =1.43, 95% CI =1.26- 1.62 ), with all associations being statistically significant ( P <0.05). After adjusting for confounding factors, boys who ate breakfast away from home showed a significantly reduced risk of undernutrition ( OR =0.80,95% CI =0.66-0.97), while those consuming lunch away from home had an increased risk ( OR =1.26, 95% CI =1.01-1.57) ( P <0.05). Conclusions The choice of dining locations for children is becoming more diverse, and a relatively high proportion of children eat meals outside the home and at school. Eating out have a higher risk of malnutrition for children. School feeding may be beneficial to children s physical health.

Objective: To analyze the relationship between vitamin D and ferritin nutritional status with physical indicators in primary and secondary school students in the key nutrition monitoring counties of Xinjiang, so as to provide reference for early prevention and intervention of students nutrition issues. Methods: From November to December 2023, 1 071 students aged 6-18 from key nutrition monitoring counties in the Xinjiang Nutrition Improvement Plan area were selected via stratified random sampling for physical and biochemical tests. The U test and Kruskal-Wallis H-test were used to compare the differences in physical indicators and the distribution of vitamin D and ferritin levels. Chi-square test was used to compare the prevalence of vitamin D and ferritin deficiencies among different groups of primary and secondary school students. Pearson correlation was used to analyze the relationship between the nutritional levels of vitamin D and ferritin and physical indicators. Results: The median vitamin D level was 14.7 (10.7, 19.0)ng/mL, with deficiency and insufficiency rates of 30.8% and 37.4% among primary and secondary school students in the key nutrition monitoring counties of Xinjiang Nutrition Improvement Plan area. Ferritin levels were 57.4 (37.7, 83.9)μg/L, with a deficiency rate of 5.7%. Males, primary school students, and rural residents had higher vitamin D and ferritin levels than females, secondary school students, and urban residents ( U =-11.35, -6.88, -4.52; -3.94, -9.17, -5.23, P <0.05). Vitamin D deficiency was more prevalent in females, secondary school students, and urban students ( χ 2=97.52, 49.01, 21.89, P <0.05), while ferritin deficiency was higher in primary school students and urban areas ( χ 2=34.11, 5.63, P <0.05). Significant differences in body mass index (BMI) and waist circumstance (WC) were observed across vitamin D/ferritin statuses ( U/H =35.47, 22.82; -4.19 , -5.36, P <0.05). Vitamin D and ferritin levels negatively correlated with age, BMI, and WC but positively with waist-to-height ratio (WHtR) ( r = -0.31, -0.19, -0.19, 0.20; -0.32, -0.13, -0.21, 0.08, P <0.05). Conclusions Vitamin D and ferritin levels in primary and secondary school students in key nutritional monitoring counties in Xinjiang are correlated with age, BMI, WC and WHtR, and there are nutrient deficiencies. Targeted measures are recommended to improve nutritional status and physical health.

Objective: To investigate the nutritional status and influencing factors among Tibetan and Mongolian children and adolescents aged 7-18 years in high-altitude regions, so as to provide evidence for early prevention and control of malnutrition in this population. Methods: From May to June 2022, a cluster sampling method was employed to recruit 1 019 Tibetan and Mongolian children and adolescents aged 7-18 years from two primary and secondary schools in Golmud City. Physical examinations, dietary frequency questionnaires, and physical activity assessments were conducted. Nutritional status was classified as obesity, combined overweight/obesity, underweight, or central obesity according to national standards including Screening for Overweight and Obesity among School-age Children and Adolescents, Screening Standard for Malnutrition of School-age Children and Adolescents, Blue Book on Obesity Prevention and Control in China. Chi-square tests, t-test and Logistic regression analyses were performed to identify factors associated with different nutritional statuses. Results: The detection rates of obesity, combined overweight/obesity, underweight, and central obesity were 8.0%, 18.1%, 5.2%, and 19.7%, respectively. The height of children and adolescents across all age groups was generally lower than the national standard values. Tibetan participants exhibited significantly lower height-for-age Z-scores (HAZ)(9-10, 13-17 years, Z =2.01, 2.78, 4.16, 3.38, 4.12, 3.63, 3.00) and BMI-for-age Z-scores (BAZ) compared to Mongolian participants ( Z =-2.95, -2.47, -2.31, -2.89, -2.14, -2.17)( P < 0.05 ). Multivariate Logistic regression revealed that Mongolian children and adolescents had higher risks of obesity ( OR =2.20) and combined overweight/obesity ( OR = 2.18 ) ( P <0.05). Additionally, insufficient moderate-to-vigorous physical activity (MVPA) was associated with an increased risk of central obesity ( OR =1.48, P <0.05), compared with children and adolescents who meet the standard of MVPA. Conclusions The rates of overweight and obesity among Tibetan and Mongolian children and adolescents in Golmud City are higher, influenced by multiple factors. Nutrition interventions and physical activity strategies tailored to ethnic characteristics should be implemented, with emphasis on promoting MVPA to improve nutritional outcomes in this population.