OP56 Longitudinal effects of peer victimization during childhood on overweight and internalizing disorders in late adolescence [Abstract]

Sum, Ka Kei, Daniel, Rhian M. ORCID: https://orcid.org/0000-0001-5649-9320, Heron, Jon E., Herbert, Annie and Howe, Laura D. 2026. OP56 Longitudinal effects of peer victimization during childhood on overweight and internalizing disorders in late adolescence [Abstract]. Journal of Epidemiology and Community Health 80 (S2) , p. A28. 10.1136/jech-2026-ssmabstracts.56

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Abstract

Background Peer victimization in childhood can have lasting impacts on physical, mental, and social outcomes. Bidirectional relationships between peer victimization and internalizing disorders or overweight status suggest the presence of time-dependent confounding, which can bias conventional longitudinal analyses. Few studies have estimated the causal effects of peer victimization while appropriately accounting for such confounding. Methods Peer victimization was assessed at age 8, 10, and 12 years using validated questionnaires among 8808 individuals from the Avon Longitudinal Study of Parents and Children (ALSPAC) in Southwest England. Internalizing disorders were measured at age 17 years using the Clinical Interview Schedule-Revised (CIS-R), with primary outcome defined as any depression or anxiety. Overweight status at age 17 years was defined based on body mass index z-scores derived from the 1990 British Growth Reference. Marginal structural models with stabilized inverse probability weights were used to estimate population-average total effects (sum of direct and indirect effects), controlled direct effects (effects not mediated through later exposures), and joint effects of peer victimization trajectories on internalizing disorders and overweight status. We also evaluated the effects of hypothetical stochastic interventions that reduce peer victimization by 15%, 25% and 40% across childhood using a longitudinal modified treatment policy. Results Peer victimization at age 12 was estimated to have the largest total effect on internalizing disorders (depression / anxiety) at age 17, particularly among females (OR = 1.70 [1.28, 2.25]). Estimates of total and controlled direct effects at ages 8 and 10 years were less precise across both sexes. The relative risk reduction was about 40% (RR = 0.58 [0.38, 0.78]) had females followed a trajectory of no victimization compared with persistent victimization, with risk reductions also estimated when victimization ceased by age 10 or 12. Hypothetical stochastic interventions reducing peer victimization corresponded to 2-9% lower estimated relative risks of internalizing disorders in a dose-response manner, compared with no intervention. There was little evidence of effects on overweight status. Conclusion Peer victimization across childhood and early adolescence appears to increase the population-level risk of internalizing disorders, with exposure during early adolescence exerting the strongest influence. Preventing peer victimization and reducing its persistence may meaningfully lower the risk of internalizing disorders at the population level.

Item Type:	Short Communication
Date Type:	Published Online
Status:	Published
Schools:	Schools > Medicine
Publisher:	BMJ Publishing Group
ISSN:	0143-005X
Last Modified:	16 Sep 2026 08:45
URI:	https://orca.cardiff.ac.uk/id/eprint/189644

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