PROJECT SUMMARY This project seeks to shed light on mechanisms underlying transdiagnostic risk for mental illness byintegrating two traditionally disparate lines of research. One line of work indicates that repetitive negativethinking (RNT)a transdiagnostic risk factor characterized by frequent negative self-focused thoughtsincreases vulnerability for a range of mental health disorders including depression and anxiety. A second lineof work demonstrates that high-quality social relationships are associated with lower rates of mental andphysical illness; conversely relationship stress hostility and disconnection exacerbate loneliness isolationand mental and physical illness. This proposal will test a new model in which RNT and social connectednesswork together as parts of an integrated whole. The central argument of this model is that RNT exerts itspernicious effects on mental health by impairing the ability to meaningfully connect with others throughempathya critical component of social connection that involves sharing and understanding others emotions.Critical to this model is the hypothesis that RNT and empathy operate dyadically; that is they affect bothpartners in a close relationship. To test this model this project will implement a multilevel research design thatintegrates self-report neuroimaging and naturalistic observation to study RNT social connection and mentalhealth in the context of established close relationships. Specifically the project will employ a multi-methodapproach across 200 established romantic couples (young adults to those in middle age; N = 400) to assessthe following aims: (1) Examine associations between RNT and partner-directed neural and behavioralempathy among romantic couples; (2) Determine the role of neural empathy in dyadic social-emotional andmental health outcomes; (3) Determine the role of RNT in dyadic mental health outcomes; and (4) Examinewhether neural empathy mediates the dyadic association between RNT and longitudinal mental healthoutcomes. Advancing prior work the proposed research will examine neural empathy in a novel and validatedsocial feedback task using functional MRI in each member of the couple to be modelled using dyadicstatistics. Additionally RNT and daily social behaviors will be assessed in everyday life using two mobile appsdeveloped by the research team: Mind Window and the Electronically Activated Recorder (EAR). Finallymental health will be assessed over 6 months to allow for prospective changes in the primary outcomes ofinterest. To tackle the studys aims this proposal brings together an interdisciplinary team of researchers withexpertise spanning all facets of the proposed research: RNT depression neural empathy socialconnectedness dyadic modelling and ambulatory assessment. Ultimately this work holds promise foradvancing scientific understanding of how individual and social risks for psychopathology operate together toshape emotional disorders. In turn this research has the potential to help identify novel intervention targets tostrengthen social connectedness in service of improving mental health.