The trajectory of depression and anxiety among children and adolescents over two years of the COVID-19 pandemic

•On average, children and adolescents experienced sustained symptoms of depression and anxiety over the two years of the COVID-19 pandemic.•Evidence of adaptation to pandemic-related restrictions across the first two years of the pandemic is not observed.•Among children with pre-pandemic depression data, a significant increase in depression symptoms was observed relative to pre-COVID levels. Longitudinal research examining children's mental health (MH) over the course of the COVID-19 pandemic is scarce. We examined trajectories of depression and anxiety over two pandemic years among children with and without MH disorders. Parents and children 2-18 years completed surveys at seven timepoints (April 2020 to June 2022). Parents completed validated measures of depression and anxiety for children 8-18 years, and validated measures of emotional/behavioural symptoms for children 2-7 years old; children ≥10 years completed validated measures of depression and anxiety. Latent growth curve analysis determined depression and anxiety trajectories, accounting for demographics, child and parent MH. Data were available on 1315 unique children (1259 parent-reports; 550 child-reports). Trajectories were stable across the study period, however individual variation in trajectories was statistically significant. Of included covariates, only initial symptom level predicted symptom trajectories. Among participants with pre-COVID data, a significant increase in depression symptoms relative to pre-pandemic levels was observed; children and adolescents experienced elevated and sustained levels of depression and anxiety during the two-year period. Findings have direct policy implications in the prioritization and of maintenance of educational, recreational, and social activities with added MH supports in the face of future events.