Age and sex differences in the effects of peer victimization on depressive symptoms: Exploring sleep problems as a mediator

•We explored a novel mechanism linking peer victimization to depressive symptoms through sleep problems and determined whether this pathway varied by age and sex of adolescents.•Sleep problems mediated the effects of peer victimization on depressive symptoms in females only.•Age moderated the mediational pathway from peer victimization to depressive symptoms through sleep problems in females.•Improving sleep problems may be one important strategy to decrease depressive symptoms in female adolescents with experiences of peer victimization, especially in older female adolescents. Peer victimization contributes to an elevated risk of adolescent depression. Although theoretical evidence has noted that peer victimization may disrupt sleep and subsequently increase levels of depressive symptoms, this pathway has never been tested. This study explores a novel mechanism leading from peer victimization to depressive symptoms through sleep problems and considers whether the direct and indirect pathways vary by age and sex of adolescents. Data were from 4072 adolescents (2042 males, 2030 females; age range 14–19 years) residing in northern Taiwan. Mediation analyses were first conducted to understand the mediating role of sleep problems in the association between peer victimization and depressive symptoms for males and females, respectively. Moderated mediation analyses were then applied to test age differences in the direct and indirect pathways from peer victimization to depressive symptoms. Sleep problems mediated the association between peer victimization and depressive symptoms in adolescent females but not in males. Age further moderated the indirect pathway from peer victimization to depressive symptoms through sleep problems, such that the mediating effects of sleep problems increased with age and were only significant in older females. No age differences were observed for the direct effects of peer victimization on depressive symptoms in either males or females. Study was not designed to infer causality and all variables were assessed by self-report measures. Our analyses revealed age and sex differences in the link from peer victimization to depressive symptoms through sleep problems. Efforts to reduce depressive symptoms in adolescent females who have experienced peer victimization may be made more effective by targeting sleep problems, especially in older female adolescents.