Research has demonstrated the transdiagnostic importance of irritability in psychopathology pathways but the contribution of developmentally-unfolding patterns has only recently been explored. To address this question, irritability patterns of 110 youth from a large and diverse early childhood cohort were assessed at preschool age and at school age (~2.5 years later) with a dimensional irritability scale designed to capture the normal:abnormal spectrum.Participants then returned at Pre-adolescence (~6 years later) for an assessment with a structured clinical interview (internalizing/externalizing symptoms) and a magnetic resonance imaging scan. When only preschool age irritability was considered, this was a transdiagnostic predictor of internalizing and externalizing symptoms. However, a model including both preschool and school age irritability provided a more nuanced picture. A high preschool and decreasing school age profile of irritability predicted elevated pre-adolescence internalizing symptoms, potentially reflecting emerging coping/internalizing behavior in pre-adolescence. In contrast, a stable irritability profile across these timepoints predicted increased pre-adolescence externalizing symptoms. Further, preschool irritability (a period of rapid growth) did not predict preadolescent gray matter volume abnormality, an indicator of transdiagnostic clinical risk.However, irritability at school age (when gray matter volume growth is largely finished) demonstrated an interactive effect among regions; increased school age irritability predicted reduced volume in pre-adolescence emotional regions (e.g., amygdala, medial orbitofrontal cortex) and increased volume in other regions (e.g., cerebellum). Expanding the impact of RDoC's approach yielding transdiagnostic phenotypes and multiple units of analysis, a developmentally informed approach provides critical new insights into the complex unfolding of mechanisms underlying emerging psychopathology.
IRRITABILITY PREDITS CLINICAL OUTCOMES/GRAY MATTER VOLUMES