Body mass index and depressive symptoms in adolescents in Taiwan: testing mediation effects of peer victimization and sleep problems

BACKGROUND: Despite recognition of the link between body mass index (BMI) and depression in adolescence, the underlying mechanisms behind this association remain understudied. This study aims to examine three mediational pathways from BMI to depressive symptoms through peer victimization and sleep problems. Sex differences in the mediating effects were also explored. METHODS: Data came from 1893 adolescents participating in a multi-wave longitudinal study from grade 9 to 12 in northern Taiwan were analyzed. Measures included BMI in 2009, peer victimization in 2010, sleep problems in 2011, depressive symptoms in 2012 and other covariates (sex, age, parental education, family structure, family economic stress, stressful life events, pubertal development and previous scores of focal study variables). A series of multiple regression models were conducted to test mediation hypotheses. A bootstrapping approach was applied to obtain confidence intervals for determining the significance of indirect effects. RESULTS: The association between BMI and depressive symptoms was significantly mediated by peer victimization and sleep problems. Higher BMI predicted more peer victimization and sleep problems, each of which led to higher levels of depressive symptoms. Our results further showed that higher BMI was associated with more peer victimization, which led to greater sleep problems and in turn resulted in increased depressive symptoms. No sex differences was found for the indirect effects of BMI on depressive symptoms through either peer victimization or sleep problems. CONCLUSIONS: Peer victimization and sleep problems partly explain the link between BMI and depressive symptoms. Interventions to prevent or manage depressive symptoms may yield better results if they consider the effects of these two psychosocial factors rather than targeting BMI alone.