OBJECTIVETo investigate the relationship between traditional bullying, cyberbullying and depression in adolescents, with the involvement frequency and different roles considered.

METHODSA stratified cluster sampling method was used to randomly select 5 726 middle school students in three cities of Anhui province in December 2013. Those students were surveyed by self-designed questionnaire of adolescent health-related behaviors in Anhui province. Self-reports on the general demographic information, physical, verbal, relational bullying and cyberbullying involvement and depression were collected. Additionally, the items assessing depression were based on Self-rating Depression Scale (SDS). The chi-square test used to compare prevalent rates of bullying involvement and depression in different groups of students with different demographic features. Multinomial logistic regressions were performed to explore the relationships between all four types of bullying and depression, after controlling confounders.

RESULTSWe got a final effective sample of 5 726 student. The response rate was 99.4% in this study. Among 5 726 adolescents, the prevalence rates of bullying in the last two months were 23.4% (1 339/5 726) physically, 55.0% (3 147/5 726) verbally, 34.2% (1 958/5 726) socially, and 8.9% (512/5 726) electronically. The prevalence rate of depression was 64.8% (3 711/5 726). The detection rate was higher in participants who involved in physical, verbal, relational, and cyber bullying than those who not involved in bullying. After controlling the confounding factors, the different frequency and role of verbal and relational bullying were risk factors of depression (OR = 1.42-3.71, all P values < 0.001). As for physical bullying, except for occasional bully-victims (OR = 1.08, 95% CI: 0.79-1.49), others were more likely to be depressed than noninvolved students. (OR = 1.40-7.84, all P values < 0.001). Frequent involvement in cyberbullying as bullies and (or) victims were more likely to be depressed than noninvolved students (OR = 2.30-4.55, all P values < 0.001), but occasional involvement in cyberbullying as bullies and (or) victims were not the risk factors of adolescents' depression (OR = 1.39, 95% CI:0.97-1.99; OR = 1.58, 95% CI: 0.88-2.82; OR = 1.50, 95% CI:0.82-2.74).

CONCLUSIONInvolvement in physical, verbal, relational, and cyberbullying were risk factors for depression among adolescent students.