Changes in peer and sibling victimization in early adolescence: longitudinal associations with multiple indices of mental health in a prospective birth cohort study.

Victimization by peers and siblings is associated with poorer mental health outcomes in adolescence. What is less clear is whether mental health outcomes improve if victimization experiences cease (e.g., being victimized in primary school but not secondary school). This study aims to explore how changes in victimization experiences are associated with changes in mental health outcomes in early adolescence. Data are from 13,912 participants in the Millennium Cohort Study (MCS), a nationally representative cohort of individuals born in the UK. Self-reported victimization by peers and siblings, as well as mental health outcomes (depressive symptoms, life satisfaction, self-esteem, and body image), were collected at age 11 and age 14. Victimization at either time point was associated with poorer mental health across the range of outcomes, with effects largest for those who were consistently victimized. Those who reported increasing victimization had greater deterioration in their mental health compared with their peers who were never victimized. Conversely, children whose victimization decreased showed similar mental health development over this period as those who were never victimized. There was a cumulative effect of victimization by peers and siblings, with effect sizes generally larger for experiences with peers. Victimization in adolescence is associated with enduring reductions in mental health. Nonetheless, the promising outcomes associated with reductions in victimization suggest the potential for bullying interventions in schools to limit the deterioration in mental health in victimized groups.