The longitudinal course of childhood bullying victimization and associations with self-injurious thoughts and behaviors in children and young people: A systematic review of the literature.

INTRODUCTION: Bullying victimization has consistently been highlighted as a risk factor for self-injurious thoughts and behaviors (SITBs) in young people. This systematic review of prospective, community-based studies explored associations between bullying victimization (traditional/face-to-face and cyber) across the full spectrum of self-harm and suicidality, in children and young people aged up to (and including) 25 years. Importantly, associations by sex/gender were explored. METHODS: MEDLINE, Embase, PsycINFO, CINAHL and Scopus were searched for articles meeting the inclusion criteria. Articles were screened by title, abstract and full text. Quality appraisal was performed using the Newcastle-Ottawa Scale for cohort studies. Data were synthesized narratively. The protocol is registered on PROSPERO (CRD42021261916) and followed PRISMA 2020 guidelines. RESULTS: A total of 35 papers were included, across 17 countries. Results were presented by bullying type: traditional/face-to-face (n = 25), cyber (n = 7) and/or an aggregate of both types (n = 7). Outcomes included suicidal ideation (n = 17), self-harm (n = 10), suicide attempt (n = 4), NSSI (n = 4), other (n = 7). Studies measured outcomes in under 18s (n = 24), 18-25-year-olds (n = 8) and both under 18s and 18-25-year-olds (n = 3). Studies exploring the role of sex/gender (20%) found some interesting nuances. CONCLUSIONS: Some weak to strong associations between bullying and SITBs were found yet conclusions are tentative due to study heterogeneity (e.g., methods used, conceptualizations and operationalisations of exposures/outcomes). Future research should address methodological issues raised in this review, and further explore gender differences in bullying, including by bullying sub-types (e.g., overt or relational) and victim status (e.g., victim or bully-victim).