To examine the independent and interactive associations of being bullied and non-suicidal self-injury (NSSI) with suicidal behaviors (suicidal ideation, suicidal plan, and suicidal attempt) among junior and senior high school students in China. A cross-sectional study was conducted in 4 cities from November 2017 to January 2018 and a total of 18,900 students were enrolled in this study. Being bullied, NSSI and suicidal behaviors were measured by self-reported questionnaires. Analyses were conducted with Chi-square tests, multivariable logistic regression, and additive interaction models. Results showed that the prevalence of suicidal ideation, suicidal plan, and suicidal attempt was 26.4%, 13.2% and 5.2%, respectively. Being bullied was significantly associated with suicidal ideation (OR = 2.35, 95% CI: 2.17–2.55), suicidal plan (OR = 2.25, 95% CI: 2.03–2.48) and suicidal attempt (OR = 2.27, 95% CI: 1.96–2.62). NSSI was significantly positively correlated with suicidal ideation (OR = 3.92, 95% CI: 3.64–4.21), suicidal plan (OR = 3.72, 95% CI: 3.39–4.08) and suicidal attempt (OR = 3.29, 95% CI: 2.86–3.79). Additive interaction models indicated that NSSI was associated with an increase in the risk of suicidal behaviors among adolescents being bullied than those not being bullied. Namely, additive interactions of NSSI and being bullied on suicidal behaviors were found. The NSSI and being bullied have synergistic effects, and co-victimization, rather than single. Meanwhile, considering the perpetrator is critical to intervening suicidal behaviors in adolescence. Ideally, intervention programs should take action from multiple aspects according to different types of factors, including individual level, social environment and institution.
