Aberrant personal space is associated with paranoia, altered stress regulation, and unfavourable outcomes at 6 months' follow-up in schizophrenia.

Paranoia is a central feature of schizophrenia and linked with poor outcomes. Paranoid experience is sometimes hard to identify in the clinical interview. In contrast, personal space (PS) measures detected patients with paranoia with excellent sensitivity and specificity. Here we test whether we can substantiate aberrant PS regulation in paranoia and whether PS was associated with stress markers and longitudinal outcomes. We included 144 participants (92 patients with schizophrenia spectrum disorders and 52 age and sex-matched healthy controls). We measured PS and stress markers during two behavioural tasks on interpersonal distance. In addition, we assessed social outcomes at baseline and after 6 months. Data corroborated that paranoia increased PS. Moreover, we confirmed that PS detected paranoia with excellent sensitivity (92%) at 1.1 m, and severe paranoia with 87% sensitivity and 81% specificity at 1.6 m. In addition, stress (Electrodermal activity) during the PS task was associated with paranoia and PS. Furthermore, higher stress at baseline predicted less improvement of social outcome after 6 months. Finally, improvement of PS over 6 months was associated with improvement of social functioning. PS may indeed serve as a simple bedside test for paranoia. Furthermore, results have direct implications in clinical practice as they suggest that it is advisable to maintain increased PS with paranoid patients. In addition, altered stress regulation and persistently increased PS may indicate unfavourable outcomes in the short-term follow-up. Thus, patients with persistently increased PS may benefit from special therapeutic attention.