Association between Body Mass Index and Externalizing and Internalizing Symptoms among Chinese Adolescents: Mediating Role of Traditional Bullying and Cyberbullying Victimization

Background: Externalizing problems, internalizing problems, and obesity are among the greatest challenges to adolescent health. However, the moderating and mediating mechanisms that underlie this association remain predominantly unexplored. Objectives: In this study, we examined the association between body mass index (BMI) and externalizing and internalizing scores in adolescents, tested whether traditional bullying and cyberbullying mediated the association, and explored the moderated role of sex. Methods: The data came from 1486 adolescents from grade 7, 8, and 10 living in Shantou, China. Information on BMI, traditional bullying, and cyberbullying victimization was obtained through a self-administered questionnaire. The students' externalizing and internalizing scores were evaluated using the Strengths and Difficulties Questionnaire (SDQ). Furthermore, we built two parallel mediation models with sex as a moderating variable. Results: Compared to their peers with normal weight, adolescents with increased BMI reported higher externalizing and internalizing scores. Traditional bullying and cyberbullying were both significant mediators in the two relationships. Sex moderated the pathway from BMI to cyberbullying. But sex did not moderate the relationship between BMI and traditional bullying. Conclusions: The results highlight that it is imperative for educators to identify students who are subjected to weight-based bullying and provide them with recommendations for effective coping strategies. Meanwhile, both victims of traditional bullying and those affected by cyberbullying should be the focus of prevention and intervention efforts when developing a strategy to improve levels of internalizing and externalizing symptoms among adolescents with increased BMI.