Understanding and Assessing Pediatric Irritability: Developmental Trajectories, Convergent Validity, and Multi-level Risks - PROJECT SUMMARY/ABSTRACT Irritability is a significant and widespread issue among youth, affecting up to 20% and prompting treatment- seeking in 58% of cases. It disrupts daily functioning and predicts long-term problems such as academic difficulties, poverty, and suicidality. Transdiagnostic in psychiatric classification, irritability spans multiple disorders including depression, anxiety, and oppositional defiant disorder. Despite the profound public health implications of irritability, no research tracks irritability from early childhood to late adolescence, a time of profound changes. Existing studies focus on narrow age ranges and don’t often include diverse populations. Moreover, the field relies solely on caregiver reports, neglecting a multi-method approach. While initial data shows promise in caregiver reported, observational, and physiological indicators of irritability, no research has tested the convergent validity of these methods for a more comprehensive assessment of irritability in youth. Finally, despite a wide range of risk factors linked to youth mental health, several factors that may influence irritability remain poorly understood and underexplored. This application will analyze secondary data and conduct a brief online follow-up survey from the Kids Markers Study (KMS), a sample of 245 children exposed to maltreatment and matched controls. KMS provides data on irritability across development and relevant early childhood risk factors. The new component in this F32 proposal is caregiver-reported irritability in late adolescence (N=100; ages 16-19). The overall aims of this study are to investigate developmental trajectories of irritability from early childhood through late adolescence, establish the convergent validity of various indicators (caregiver, observational and physiological arousal) of irritability, and explore multilevel (child, family, and environmental) risk factors of irritability. This innovative study will contribute to understanding the dynamic nature of irritability, aiming to pave the way for more effective interventions and policies. This study utilizes comprehensive assessments of early childhood child, family, and environmental risk factors, along with novel approaches to measuring irritability, such as respiratory sinus arrhythmia (RSA) and a caregiver-child interaction task. This highly structured training plan will allow the applicant to 1) Develop expertise in conducting translational, developmentally informed research on child, family, and environmental risk factors impacting irritability; 2) Gain expertise in observational coding of caregiver-child interactions, focusing on irritability-related behaviors; 3) Master advanced physiological data processing and analysis techniques; 4) Learn advanced statistical methods for testing developmental and biopsychosocial research questions; and 5) Enhance autonomy in presenting scientific work, preparing manuscripts, and writing grant proposals. Guided by an outstanding mentorship team with relevant expertise and a history of collaboration, the training and research plans at the Department of Psychiatry and Human Behavior of the Warren Alpert Medical School of Brown University offer a tailored environment to support the applicant in becoming an independent investigator.