Trajectory of irritability in children and youth in Ontario, Canada, throughout the COVID-19 pandemic.

Background: Children and youth have been greatly affected by the COVID-19 pandemic. The current study explored trajectories of irritability across the pandemic and associations with mental health outcomes. Models included risk and protective factors; age, gender, ethnicity, family income, pre-existing mental health condition, parental mental health, and resilience. Methods: The study included 905 children and youth (mean age: 11.85, SD: 2.92, range: 8-17 years old: male: 55%) from the longitudinal Ontario COVID-19 and Kids Mental health Study. Irritability was measured based on parent and self-reports over seven time points from April 2020 to June 2022. Latent growth curve modeling captured the initial level of irritability with the intercept and change over time with the slope as the latent factors, which were in turn used to predict internalizing and externalizing mental health outcomes using multiple regression. Results: Model fits for both parent-report and self-report data were satisfactory, showing an initial increase (only in parent-report data) and a linear decrease overtime. In both models, having a younger age, female gender (only in self-report), higher parental anxiety, positive mental health history and lower resilience were significantly associated with higher initial irritability level ( Conclusion: The results showed that pediatric irritability levels were sensitive to the COVID-19 pandemic, and generally decreased over time. Risk and protective factors mostly affected the initial level while age was associated with the change of irritability over time. Early signs of irritability, especially among those high-risk groups, could potentially inform patterns of mental health outcomes in the face of adversity as a potential target for early intervention for clinicians and educators.