Project Summary Psychiatric illnesses affect millions of Americans and can be associated with substantial emotional and financial hardship for both those who are affected and their families. In fact, these illnesses are responsible for a substantial portion of the disability associated with chronic medical conditions overall, in large part because they 1) tend to be persistent or recurring throughout the lifespan, and 2) often lead to impairments in day-to- day functioning. However, despite these well-known consequences of psychiatric conditions, there are still very few validated, evidence-based, transdiagnostic interventions that are explicitly focused on the prevention of the onset of these conditions and the associated disability. Thus, in this application, we propose to conduct a randomized clinical trial of a four-session, group-based behavioral intervention called Resilience Training (RT) that was previously shown in a randomized, waitlist-controlled trial to significantly reduce levels of subthreshold symptoms of psychosis (often called “psychotic experiences” or PEs) and other transdiagnostic symptoms of psychiatric illnesses in young adults (college students) with these symptoms. It has been well-established that the presence of subclinical psychopathology including PEs is associated with an increased risk for the subsequent development of a range of psychiatric illnesses, including psychotic, mood, anxiety and substance use disorders, as well as suicidal behaviors and functional impairment. Therefore, in the proposed trial, we will test whether RT leads to reductions in PEs and the distress associated with them, and reductions in anxiety, depression and suicidality, in young adults with PEs, over a two year period. This trial will also investigate whether RT leads to a reduction in emotion reactivity, a reflection of stress sensitivity, and improves the functional connectivity and function of the hippocampus, a brain region involved in the body’s responses to stress. Moreover, this project will evaluate whether RT positively impacts objective outcomes in college students that reflect academic functioning and psychological health, including course credits earned, retention in college and use of psychiatric crisis services, in addition to clinical outcomes, such as symptom levels and the onset of psychiatric disorders. Lastly, the project will test whether the predicted mediating mechanisms of RT (the reduction in emotion reactivity and improvements in hippocampal connectivity and function) are responsible for any of its positive effects on functional and clinical outcomes. Overall, if the preventive efficacy of RT is demonstrated, the results of this study will lay the foundation for dissemination of RT within a wide range of communities where young people spend their time, on college campuses as well as in vocational and employee training programs, primary care clinics, and work settings.