Consistency of Delusion Themes Across First and Subsequent Episodes of Psychosis.

Importance: Despite growing interest in the phenomenology of delusions in psychosis, at present little is known about their content and evolution over time, including whether delusion themes are consistent across episodes.

Objective: To examine the course of delusions and thematic delusion content across relapse episodes in patients presenting to an early intervention service for psychosis.

Design, setting, and participants: This longitudinal, observational study used clinical data systematically collected from January 2003 to March 2018 from a cohort of consenting patients with affective or nonaffective first-episode psychosis, followed up naturalistically for up to 2 years in an early intervention service for psychosis in Montréal, Quebec, Canada. Data included the thematic content and severity of delusions (scores ≥3 using the Scale for the Assessment of Positive Symptoms) and associated psychotic and nonpsychotic symptoms, both across an initial episode and, in the event of remission, a potential relapse. Data were analyzed from September 2021 to February 2023.

Exposure: An early intervention service for psychosis, organized around intensive case management and a multidisciplinary team approach, which observed each patient for up to 2 years of care.

Main outcomes and measures: The primary outcome was positive symptom relapse and remission, including the presence and content of delusions, which was coded per the Scale for the Assessment of Positive Symptoms and accepted definitions. The main statistical measures included repeated paired-sample t tests and binary logistic regression analyses.

Results: Of 636 consenting patients, mean (SD) age was 23.8 (4.75) years; 191 patients were female, 444 were male, and 1 patient was nonbinary. Remission rates were high, and relapse rates were relatively low: 591 individuals had baseline delusions, of which 558 (94.4%) achieved remission. Of these 558 patients, only 182 (32.6%) had a subsequent relapse to a second or later episode of psychosis. Of the 182 patients who did relapse, however, a large proportion (115 [63.2%]) reported threshold-level delusions. Of these 115, 104 patients (90.4%) had thematic delusion content consistent with that reported during the index (first) episode. Those who relapsed with delusions had fewer delusion themes present during subsequent episodes of psychosis compared with the index episode and lower levels of other psychotic and nonpsychotic symptoms.

Conclusions and relevance: Specialized early intervention services for psychosis can achieve high rates of sustained remission. However, in this study, the minority of individuals with delusions who later relapsed experienced similar delusion themes during subsequent episodes. These findings raise important considerations for the conceptualization of delusions and have clinical implications for trajectories of illness and care.