Abstract Mental health problems among adolescents have been a major concern worldwide. Physical activity shows beneficial effects on mental health issues. The paper reviewed domestic and foreign literature on the association between physical activity and mental health problems in adolescents, and further explored the separate role of individual psychological, social and biological factors in the association, providing reference for mental health promotion among adolescents.

Objective: To explore the associations between sleep duration and negative emotions among junior college students,and to provide reference for mental health promotion among college students. Methods: Cluster sampling method were used to select 2 524 freshmen from a college in Huainan, Anhui Province. Questionnaires were used to investigate general demographic characteristics, sleep timing, negative emotions and other information. The restricted cubic spline and multivariate Logistic regression were used to analyze the relationship between sleep duration and negative emotion among junior college students. Results: The prevalence of depressive symptoms, anxiety symptoms, stress associated symptoms were 19.41%(490), 28.2%(713), 9.9%(250) respectively．The prevalence of negative emotions was higher among boys(24.3%,34.0%,19.1%) than girls(18.7%,27.4%,8.5%). The differences between groups were statistically significant( P <0.01). After adjusting for confounding factors, sleep duration and negative emotions showed a non linear dose response relationship. Compared with the reference group(8-<9 h), sleep duration <7 h was significantly associated with an increased risk of depressive symptoms and stress symptoms, and <8 h was associated with an increased risk of anxiety symptoms. The additional sleep time on weekends ≥5 h was associated with negative emotions compared with the reference group(<1 h)( P <0.01). Conclusion Short sleep duration and extra weekend sleep are associated with negative emotions. Reasonable sleep schedule among junior college students might be helpful for the prevention and control of negative emotions.

Objective: To explore the mediating effect and gender difference of mobile phone use in the association between different types of childhood abuse experiences and sleep quality of medical students, so as to provide reference for promoting sleep quality of medical students. Methods: A longitudinal study design method was used to select freshmen and sophomores in two medical colleges in Anhui Province from November to December 2019, follow up data were collected from May to June 2020, and a total of 6 879 students were included in this study. Spearman correlation was used to analyze the association between baseline childhood abuse experiences, baseline mobile phone use and follow up sleep quality. Bootstrap program and Process software were applied to test the mediating effect of mobile phone use in the relationship between childhood abuse and sleep quality. Results: Childhood abuse experiences were positively correlated with mobile phone use and sleep quality score ( r = 0.27 , 0.24, P <0.01), and mobile phone use was positively correlated with sleep quality score ( r =0.31, P <0.01). In the total sample, after adjusting for confounding factors, mobile phone use played a partial mediating role in childhood abuse experiences (including emotional abuse, physical abuse, sexual abuse) and sleep quality, and the mediating effect was 18.08% (18.12%, 17.15%, 24.09%). The mediating effect of mobile phone use on the relationship between childhood emotional abuse, sexual abuse, childhood abuse and sleep quality in girls(18.32%, 28.05%, 18.24%) was higher than in boys(17.81%, 18.94%, 17.63%). Conclusion Mobile phone use has a mediating effect on the relationship between childhood abuse and sleep quality, controlling mobile phone overuse may contribute to improving the sleep quality for those who have experienced childhood abuse.