Longitudinal Evidence on Peer Victimisation and Persistent Mental Health Outcomes in Youth: A Systematic Review.

Longitudinal studies consistently demonstrate that repeated exposure to peer victimisation can have enduring consequences for children and adolescents' mental health. Documented outcomes include elevated risks of disorders such as depression, anxiety disorders, post-traumatic stress symptoms, and self-harm or suicidality, as well as broader psychosocial difficulties such as low self-esteem, loneliness, and internalising difficulties. However, prevalence estimates and effect sizes vary widely, reflecting differences in study design, measurement strategies, follow-up length, and the operationalisation of victimisation. This systematic review synthesises findings from 24 longitudinal studies to provide a comprehensive account of the mental health and psychosocial outcomes associated with peer victimisation. Evidence was strongest for depression and anxiety disorders, where multiple population-based cohorts in the United States, United Kingdom, Ireland, and Scandinavia showed robust prospective and retrospective associations, with risks amplified by repeated or persistent exposure. Peer victimisation also functioned as a traumatic stressor, predicting later post-traumatic stress symptoms, while self-harm and suicidality were elevated in several large-scale studies, though findings were less consistent. Additional work linked victimisation to later impaired well-being, including low self-esteem and internalizing difficulties. Mediators such as rumination, hostile attributions, and internalised stigma and moderators including gender, school belonging, and family support further explained heterogeneity in outcomes. By integrating findings across diverse contexts, this review clarifies the breadth and severity of long-term consequences of peer victimisation, highlighting both psychological mechanisms and contextual buffers. These insights can inform theoretical models of victimisation as a developmental risk factor and support the design of targeted prevention and intervention strategies.