Do loneliness and social exclusion breed paranoia? An experience sampling investigation across the psychosis continuum

Background: The role of loneliness and social exclusion in the development of paranoia is largely unexplored. Negative affect may mediate potential associations between these factors. We investigated the temporal relationships of daily-life loneliness, felt social exclusion, negative affect, and paranoia across the psychosis continuum. Method: Seventy-five participants, including 29 individuals with a diagnosis of non-affective psychosis, 20 first-degree relatives, and 26 controls used an Experience Sampling Method (ESM) app to capture the fluctuations in loneliness, feelings of social exclusion, paranoia, and negative affect across a 1-week period. Data were analysed with multilevel regression analyses. Results: In all groups, loneliness and feelings of social exclusion were independent predictors of paranoia over time (b = 0.05, p < .001 and b = 0.04, p < .05, respectively). Negative affect predicted paranoia (b = 0.17, p < .001) and partially mediated the associations between loneliness, social exclusion, and paranoia. It also predicted loneliness (b = 0.15, p < .0001), but not social exclusion (b = 0.04, p = .21) over time. Paranoia predicted social exclusion over time, with more pronounced effects in controls (b = 0.43) than patients (b = 0.19; relatives: b = 0.17); but not loneliness (b = 0.08, p = .16). Conclusion: Paranoia and negative affect worsen in all groups following feelings of loneliness and social exclusion. This highlights the importance of a sense of belonging and being included for mental well-being. Loneliness, feeling socially excluded, and negative affect were independent predictors of paranoid thinking, suggesting they represent useful targets in its treatment.