Symptom clusters of depression, anxiety, and ADHD show separable dimensional effects on reinforcement learning in children and adolescents

Past reinforcement learning (RL) studies implicated valence and uncertainty in modulating psychopathology effects on computational parameters. Yet, gaps persist in understanding their developmental trajectory, generalizability across contexts, and the nuanced impact of individual symptom severity that is often overlooked in case-control designs. In a sample of 122 8-to-18-year-olds of both clinical and typically developing individuals, our study found differential effects of depression, anxiety and ADHD on RL, noting reduced choice sensitivity and valence-related learning modulations in depression, uncertainty-related changes in anxiety and reduced learning in ADHD. We further deconstructed links to RL parameters according to five biologically plausible transdiagnostic symptom clusters of anhedonia, negative affect, fear, inattention and hyperactivity. Unexpectedly, many identified links revealed (inverted-)u-shaped instead of linear relationships. Our study provides evidence that symptom-related alterations in learning and decision-making manifest in children as young as 8 years old, with increasing influence of internalizing symptoms but decreasing influence of externalizing symptoms with age. Through this comprehensive approach, we aim to enhance understanding of the interplay between psychopathology, development, and RL processes, ultimately informing targeted interventions.