Pathways to Loneliness in First-Episode Psychosis: Testing the Sociodevelopmental Model - PROJECT SUMMARY/ABSTRACT Loneliness, the subjective feeling of social disconnection, has significant adverse effects on both physical and mental health, including increased anxiety, depression, risk for suicide, and even premature death. These outcomes are particularly severe among youth (ages 14-30) experiencing a first episode of psychosis (FEP), where loneliness may serve to worsen symptoms and delay recovery. Further, symptoms of FEP interact with unique developmental challenges during a time where social interaction is salient: youth with FEP often report high rates of stigma, which may compound and/or elicit experiences of loneliness. Positive symptoms (e.g., paranoid delusions) could lead to rejection from others (external stigma), while internalized stigma could worsen negative symptoms, such as amotivation, furthering social isolation and loneliness. Current research in loneliness in FEP is hindered by a lack of longitudinal data, examination of contextual factors influencing loneliness in youth (i.e., stigma), and limited consideration of developmental considerations. This project proposes a novel mixed-methods approach to investigate daily experiences of loneliness, stigma, and symptom severity in FEP. The project uses advanced quantitative methods to analyze group-level and individualized relationships between loneliness, stigma, and FEP symptom severity through the analysis of ecological momentary assessment (EMA) data. Additionally, a qualitative portion of the study will explore how the interruption of developmental milestones (e.g., as a result of hospitalization or absence from school or work) influences experiences of loneliness during an important time of social and personal development. The project’s goals are to (1) characterize the relationship between loneliness, stigma, and psychosis symptom severity at baseline, (2) explore temporal and contextual dynamics between loneliness, stigma, and psychosis symptom severity through analysis of longitudinal EMA data, and (3) highlight the age-related concerns of youth with FEP through the integration of interview data underscoring lived-experience perspectives. By taking into consideration stigma and other social and developmental factors, this research aims to deepen our understanding of loneliness in FEP, addressing a significant gap in our current knowledge. This project will also serve to enhance the applicant’s skills in rigorous mixed-methods research in early psychosis, through mentored training in social determinants of psychosis symptom severity, in tandem with sophisticated quantitative modeling and qualitative analysis. This novel research and in-depth training plan empowers an independent program of future research contributing to the investigation and development of more effective early intervention efforts in psychosis.