Relationship between school bullying and mental health status of adolescent students in China: A nationwide cross-sectional study

School bullying, as a public health problem, has been linked to many emotional disorders. However, the overall status of school bullying among adolescent students in China is unknown. This nationwide study aimed to investigate school bullying in China and evaluate the relationships between school bullying and mental health status.A total of 15, 415 middle and high school students were enrolled in this study through multistage stratified cluster random sampling. Multinomial logistic regression models were used to examine the association between school bullying and mental health status and the analysis was stratified by gender.Students were divided into four groups: 2.72%, bully/victims; 1.38%, bullies; 10.89%, victims; 85.01%, uninvolved. Compared with uninvolved students, students with anxiety symptoms, non-suicidal self-injury and suicide ideation had a higher risk of being involved in school bullying and were more likely to be bully/victims, bullies, and victims. Stratified analysis indicated that boys with anxiety symptoms and non-suicidal self-injury risks tended to be bullies, victims and bully/victims. However, for girls, bullying others or being bullied was related to anxiety symptoms and suicide ideation.Our study indicated that school bullying is still a health problem in the adolescent students of China, and is related to many mental health problems. Intervention programs are in urgent need to help the students involved in school bullying, both in terms of their mental and physical health.