Mediating effects of bullying involvement on the relationship of body mass index with social phobia, depression, suicidality, and self-esteem and sex differences in adolescents in Taiwan

The aims of this study were to examine the mediating effect of bullying involvement on the relationships between body mass index (BMI) and mental health problems, including social phobia, depression, suicidality, and low self-esteem among adolescents in Taiwan. The moderation effect of sex on the mediating role of bullying involvement was also examined. Five thousand two hundred and fifty-two students of high schools completed the questionnaires. Victimization and perpetration of passive and active bullying were assessed using the Chinese version of the School Bullying Experience Questionnaire. BMI was calculated from self-reported weight and height measurements. The Social Phobia Inventory, the Mandarin Chinese version of the Center for Epidemiological Studies-Depression Scale, the suicidality-related questionnaire from the epidemiological version of the Kiddie-Schedule for Affective Disorders and Schizophrenia, and the Rosenberg Self-Esteem Scale were applied to assess social phobia, depression, suicidality, and low self-esteem, respectively. The mediating effect of bullying involvement on the associations between increased BMI and mental health problems was examined by the Sobel test. The moderation effect of sex on the mediating role of bullying involvement was tested by the multiple-group structural equation model. Victimization of passive and active bullying and perpetration of passive bullying, but not perpetration of active bullying, had a mediating effect on the relationships between increased BMI and all four mental health problems. Sex did not have a significant moderation effect on the mediating role of bullying involvement. Bullying involvement should be a target of prevention and intervention in developing a strategy to improve mental health among adolescents with increased BMI.