The impact of the COVID-19 pandemic on the mental health of children and young people with pre-existing mental health and neurodevelopmental conditions: a systematic review and meta-analysis of longitudinal studies

Background: systematic reviews have suggested mixed effects of the COVID-19 pandemic on the mental health of children and young people. However, most included studies focused on the general population and were cross-sectional. The long-term impact on those with pre-existing mental health and/or neurodevelopmental conditions remains unclear. Thus, we conducted a systematic review and meta-analysis to examine the longitudinal impact of the pandemic on the mental health of this clinical population and potential explanatory factors.<br/><br/>Methods: Ovid Medline, Embase, APA PsycInfo, and Global Health databases were searched between 1st January 2020 and 3rd August 2023 (PROSPERO CRD42022383546). We included longitudinal studies that compared mental health symptoms between pre- and during pandemic and/or during pandemic timepoints in children and young people (≤18 years old) with pre-existing mental and/or neurodevelopmental conditions. Outcomes included internalising, externalising, and other symptoms. Risk of bias was rated using an adapted tool. Included studies were narratively synthesised and multi-level meta-analyses were conducted where the number of studies was sufficient. <br/><br/>Results: we identified 21 studies (N = 2,617) from 6,083 records. Studies differed across countries, diagnoses, measures, informants, and timepoints. All had overall moderate-to-high risk of bias. Narrative synthesis found mixed evidence of symptom change, with individual studies showing increase/reduction/no change. Factors such as diagnosis, baseline symptom severity, age, and sex/gender may explain variation in outcomes. Multi-level meta-analyses were feasible for a limited number of outcomes and found no significant changes in internalising and externalising symptoms pre- versus during pandemic or internalising symptoms between 2020 pandemic phases, and high heterogeneity was noted. <br/><br/>Conclusions: the impact of the pandemic on the mental health of children and young people with pre-existing conditions varied according to individual and contextual vulnerabilities, which were not fully captured in pooled analyses. Further research needs to investigate longer term impacts and better stratify this vulnerable population.<br/>