ABSTRACT
Objective Children's experiences of peer victimization and peer aggression are strongly linked to their mental health. However, we do not know how this relationship is influenced by periods of restricted and unrestricted social interactions. In this study we investigated a) the bidirectional association between children's peer problems and mental health;b) individual differences in the joint development of peer victimization, peer aggression and mental health and c) factors associated with joint trajectories over 13 months during the COVID-19 pandemic in the United Kingdom. Method Our sample consisted of 2160 children aged 4-10 years for whom parents/carers completed a baseline and at least one follow-up online survey between March 2020 and May 2021as part of the Co-SPACE study. We used generalized linear models to examine bidirectional associations, group-based trajectory modelling to map joint trajectories and multinomial logistic regressions to identify factors associated with trajectories. Results Experiencing mental health difficulties during school closures increased the risk of experiencing peer victimization, but not peer aggression on return to school. Experiencing any peer problems during school closures did not predict subsequent mental health difficulties. The majority of children followed joint trajectories of low exposure to peer problems and mental health, however 16-17% of our sample followed joint trajectories of high exposure to peer problems and mental health. Low family income, family conflict, parental distress, special educational needs and lack of friendships were associated with high exposure mental health and peer problem trajectories. Conclusion Increasing children's mental health support during periods of isolation may not only reduce concurrent and future mental health problems but may also prevent subsequent peer problems for both vulnerable and non-vulnerable children. Study preregistration information Co-SPACE (Covid-19: Supporting Parents, Adolescents and Children during Epidemics);https://osf.io/.