Variations in trajectories of emotional and behavioural symptoms in children and young people with pre-existing mental health and neurodevelopmental conditions before and during the COVID-19 pandemic: A nested data linkage clinical cohort study.

Background: Children and young people with pre-existing mental health and neurodevelopmental conditions may have experienced heterogeneous mental health impacts during the COVID-19 pandemic, but what facts may explain these variations are still unclear. We aimed to examine variations in the longitudinal trajectories of emotional and behavioural symptoms before and during the COVID-19 pandemic in the United Kingdom (UK). Methods: We used a novel nested clinical cohort study, linking the Maudsley Child and Young People Health and Experience Research (CYPHER) survey and electronic health records (EHRs) data of mental health service users (aged 5-17 years old) in South London and Maudsley NHS Foundation Trust, UK, on 1 June 2020 ( Results: Relative emotional and behavioural symptoms were not significantly different from pre-pandemic to 2021, but variations were found across predictors. Those who were female (vs. male; Conclusion: Emotional and behavioural symptoms were high and relatively stable across pre- and during pandemic timepoints. Relatively worse emotional and behavioural symptoms were observed in children and young people who were younger, female, lived in deprived neighbourhoods, and had a diagnosis of a neurodevelopmental condition. However, some effects might reflect distinctive features between groups rather than pandemic-specific differences. Future research should examine longer-term mental health impacts of the pandemic across clinical groups and potential mechanisms of change.