The Interplay of Mental Health Burden and Cognitive Development in Childhood and Adolescence: Insights from the ABCD Study

<title>Abstract</title> <p> Mental health disorders commonly emerge during childhood and early adolescence and are often associated with cognitive difficulties. However, longitudinal evidence examining how cumulative mental health burden relates to cognitive development in population-based samples remains limited. The purpose of this study was to evaluate the relationship between mental health burden and cognition from childhood to early adolescence. We analysed longitudinal population-based data from the Adolescent Brain Cognitive Development Study to compare cognitive performance between participants classified at baseline (9–11 years) as having (1) no mental health disorder (n = 8846); (2) one mental health disorder (n = 1406); or (3) multiple (i.e., two or more) mental health disorders (n = 434) based on the Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS) for DSM-5. Cognitive outcomes assessed using the NIH Toolbox were administered across two or three timepoints over a four-year period. Repeated measures ANOVAs tested for main effects of time and group, and time x group interactions. Across all tasks there was a significant effect of time, with effect sizes ranging from moderate to large (η ² p 0.04–0.26). There was a very small effect of group (η ² p &lt; .01) for all tasks except for picture vocabulary. The no disorder group performed significantly better than the multiple disorder groups across all tasks, and better than the one disorder group on pattern comparison processing speed. Group x time interaction effects were only observed on the picture vocabulary and pattern comparison processing speed tasks, although the effect sizes were very small (η ² p &lt; .01). These findings suggest that cumulative burden of multiple mental health disorders is associated with reduced cognitive performance. While trajectories of cognitive development from childhood to early adolescence are similar regardless of mental health burden, individuals with multiple disorders consistently exhibit poorer cognition. The magnitude of these differences is small, indicating the impact of comorbidity on cognition is modest, but persistent over time. </p>