Objective: To analyze household determinants of adolescents non suicidal self injury(NSSI), and to provide scientific basis for NSSI intervention amogn adolescents. Methods: Using stratified random cluster sampling method, 15 623 middle school students aged 11-20 were selected from Heilongjiang, Anhui, Hubei, Yunnan, and Guangdong provinces, and non suicidal self injury and related household determinants were investigated by questionnaire. Results: The survey showed that 28.8% of people who had NSSI in the past year accounted;among them,17.6% had 1-4 times(occasional self injury) and 11.2% had 5 times or more(repeated self injury) univariate results showed that whether they were an only child, family type, educational level of the main caregiver, family rearing style, family monthly income per capita, and whether there was a family history of mental illness was associated with adolescents NSSI ( χ 2=6.30-12.16, P <0.05); multivariate Logistic regression analysis showed that whether one child or family parenting style is still significantly related to occasional NSSI( OR =1.11,1.34, P <0.05)after controlling for gender, age, grade, ethnicity, emotional control, resilience, loneliness and social support; whether it is an only child, educational level of the main caregiver and family parenting style are still significantly related to repeated NSSI ( OR =1.19，0.69，1.57， P <0.05); stratified analysis by region shows that the influencing factors of NSSI in adolescents in each region are different. Conclusion Family factors such as the only child and the education level of the main caregiver may be related to the occurrence of adolescents NSSI, but there are regional differences in the family impact of NSSI.

Objective: To explore the association between aggression and social support and their gender differences among Chinese adolescence, and to provide a scientific reference for preventing and reducing aggressive behaviors of adolescents. Methods: Conducted a cross sectional survey of 15 623 adolescents in 5 provinces in China, namely, HeiLongjiang, Hubei, Anhui, Guangdong and Yunnan Province. And the Chinese version of the Adolescent Social Support Scale was employed to assess the aggression and social support, life events, psychological characteristics, family condition and demographic characteristics among adolescents. Results: The prevalence of self reported high level of aggression was 23.5%(3 670/15 623). Males reported higher rate of high level aggression than females (24.4% vs 22.5%, χ 2=19.30, P <0.01). Significant association between aggression and social support was identified in univariate analysis ( χ 2=620.68, P <0.01). After controlling for potential confounders, aggression was also significantly negatively associated with social support ( OR =1.27-1.84), and there was dose response relationship between them( P < 0.05 ). Furthermore, the association between aggression and social support was similar among male participants and female participants ( ROR =1.02-1.10, P >0.05). Conclusion The findings indicate that aggression is associated with social support both in male and female adolescents. Improving the social support for adolescents can reduce their aggressive behaviors.