PROJECT SUMMARY/ABSTRACT This experimental therapeutics R61/R33 proposal responds to RFA-MH-18-704. The goal of this project is to evaluate a new technology-supported blended intervention aimed at reducing social isolation and improving social functioning in serious mental illness (SMI). Social isolation is common in SMI and leads to morbidity and limits functional recovery. Unfortunately, few available interventions specifically target social isolation and its determinants in SMI, which include anxious social avoidance, defeatist attitudes toward interactions, and social anhedonia. Moreover, intervention development in this area is limited by imprecise measurement of social interactions, processes, and related constructs. Our new blended intervention, mobile Social Interaction Therapy by Exposure (mSITE), blends brief in-person psychotherapy with context-triggered mobile smartphone intervention and remote telephone coaching. mSITE builds on preliminary work indicating that blended mobile interventions are acceptable and both strengthen and shorten cognitive behavioral intervention. Recent work by our group and others indicates that contexts, such as being at home or alone, exacerbates social defeatist attitudes and perceptions of social threat. mSITE is unique in that it uses smartphone sensors (e.g., GPS, conversation sensing) to trigger intervention content tailored to specific social contexts, such as when home alone for extended periods or after a social interaction in the community, in order for cognitive and behavioral interventions to be delivered at the “right place, right time.” In addition, the study will be the first to examine passive sensing measures as outcomes in a clinical trial in SMI, by deriving objective digital markers of negative symptoms and social engagement using smartphone sensors (GPS and microphone) to monitor distance traveled, time spent at home, and conversations. In the R61 phase, we will recruit people with SMI who have limited social engagement. We will then conduct an open trial of mSITE, evaluating whether the intervention leads to clinically significant changes in the frequency of social interactions (the target mechanism). We will also determine the dose of app plus remote coaching necessary to achieve this effect, by evaluating change at 12, 18, or 24 weeks. If go/no go criteria are met (medium effect size increase in social interactions and < 20% dropout) in the R61 phase, the R33 phase will include a randomized trial contrasting mSITE with a therapist and device time-equivalent supportive contact (SC) condition. We will evaluate whether mSITE leads to greater improvement in social interactions, negative symptoms and social functioning relative to SC. We also predict that increases in social interactions will mediate improvements in experiential negative symptoms and social functioning. Our project responds directly to NIMH Strategic Aim 3.1, by evaluating a new behavioral intervention that targets functi...