Project Summary Anxiety disorders (ADs) are the most prevalent psychiatric ailments in children and adolescents. Childhood ADs substantially impair development and confer high risk for later psychopathology including persistent anxiety, depression and comorbid substance abuse. Given the high prevalence and long-term negative impact of childhood ADs, it is critical to successfully treat ADs early in development. Unfortunately, many children with these disorders either fail to fully respond to treatment or relapse. Understanding the biology of childhood ADs is crucial for developing early interventions with the potential to reduce the chronicity and comorbidity associated childhood onset. Cross-species conservation of brain-behavior relationships provides a unique opportunity to link basic neuroscience in nonhuman primates with clinical neuroscience in childhood ADs to identify the neural substrates of childhood anxiety. The proposed project will capitalize on this exceptional advantage by using two integrated approaches: 1) a multisite multimodal imaging study that extends promising basic science findings in nonhuman primates to a large sample of preadolescents with ADs and 2) a molecular study that translates neural findings in childhood ADs to gene expression studies in nonhuman primates using our fully-phenotyped nonhuman primate brain bank focused on alterations in neuroplasticity transcripts. Findings from our nonhuman primate studies highlight the importance of identifying neural substrates that contribute to shared variance across ADs, as well as specific neural substrates that are associated with particular anxiety phenotypes. This approach is consistent with evidence of shared and specific features of childhood ADs: most children with ADs present with an admixture of symptoms and treatment responses are similar across diagnoses suggesting shared neural substrates; however, substantial variation in symptoms and presentation suggest heterogeneous neural substrates. The study will focus on three specific aims: (1) Identify neural alterations that are shared among childhood generalized anxiety disorder, social anxiety disorder, and separation anxiety disorder; (2) determine neural alterations linked to specific anxiety-relevant RDoC constructs (i.e. acute, potential, and sustained threat, and generalization of conditioned fear); and (3) Investigate molecular alterations in brain regions central to childhood ADs, guided by the childhood AD studies in Aims 1 and 2, with a particular focus on neuroplasticity-related alterations. Studying a large sample of AD children is critical to parse the heterogeneity common in childhood ADs; to achieve this goal, we have assembled three sites with expertise in anxiety (nonhuman primate models of anxiety, childhood anxiety, developmental psychology) and advanced methods (gene expression, neuroimaging, and statistics). Ultimately we aim to elucidate the neurobiological mechanisms underlying childhood ADs to identify novel brain targets for treatment, including shared and phenotype-specific neural correlates of childhood ADs.