S101. DIFFERENTIATING NON-AFFECTIVE ACUTE REMITTING PSYCHOSIS (NARP) FROM SCHIZOPHRENIA IN FIRST-EPISODE PSYCHOSIS: FINDINGS FROM A 3-YEAR LONGITUDINAL STUDY IN THE PAFIP COHORT

BACKGROUND: The concept ‘non-affective acute remitting psychosis’ (NARP) embraces a broad set of non-affective psychotic conditions characterised by acute onset (i.e. the change from a non-psychotic to a clearly psychotic state occurred in a period of 2 weeks or less) and brief duration (less than 6 months from onset with full recovery). The prevalence of NARP ranges 5–9% of all first-episode psychosis (FEP) and, due to its limited duration and complete remission, it has generally good prognosis. However, research surrounding predictive indicators of NARP remains scarce. This study examined the clinical and sociodemographic characteristics of NARP patients, to determine whether there are early predictors that could differentiate this disorder from schizophrenia. METHODS: This research was part of a larger epidemiological 3-year longitudinal study of first-episode non-affective psychosis (PAFIP) conducted at the University Hospital Marques de Valdecilla (Spain). The sample included all patients aged 18–60 enrolled in the PAFIP programme who fullfilled NARP criteria at the end of the study period and their baseline clinical and sociodemographic characteristics were compared with those of patients with acute short-lived psychosis at admission who developed schizophrenia during follow-up. Univariate comparisons between groups were performed using Student’s t-test, Mann-Whitney’s U-test and the Chi-square test, according to distribution and variable type. Multivariate logistic regression analysis was conducted to determine the potential independent effect of each significant or marginally significant (p ≤ 0.1) variable from the univariate analysis. Statistical significance was set as p ≤ 0.05. All statistical procedures were performed using MedCalc Statistical Software (version 19.0.7). RESULTS: Of the 391 patients enrolled in the PAFIP programme between 2001 and 2018 who completed the follow-up, 31 met the criteria for NARP at the end of the study period. Mean age was 31.28 years (SD ± 9.44) and gender distribution was slightly higher for females (54.8%; n = 17). According to DSM criteria, NARP patients were classified thus: schizophreniform disorder 48.4% (n = 15), brief psychotic disorder 35.5% (n = 11) and psychotic disorder not otherwise specified 16.1% (n = 5). Univariate comparisons yielded significant differences between NARP patients and those with schizophrenia in terms of negative and activation/excitement symptomatology and in levels of insight, psychosocial functioning and premorbid adjustment. Multivariate logistic regression analysis revealed that fewer negative symptoms at admission (i.e. lower scores on Brief Psychiatric Rating Scale [BPRS] negative symptom subscale; OR = 0.75, 95% CI 0.59–0.95; p = 0.017) and better premorbid adjustment (i.e. lower scores on Cannon-Spoor’s Premorbid Adjustment Scale [PAS]; OR = 0.62, 95% CI 0.41–0.95; p = 0.011) significantly predicted the presence of NARP. Moreover, better insight into having a psychotic disorder (i.e. lower scores on Scale to Assess Unawareness of Mental Disease [SUMD]) marginally predicted NARP diagnosis (OR = 0.81, 95% CI 0.65–1.01; p = 0.056). DISCUSSION: Patients who met the NARP criteria accounted for 7.9% of FEP. Better premorbid adjustment, greater awareness of mental disorder and lower negative symptomatology at admission were independent prognostic factors that differentiated NARP from schizophrenia in FEP patients with acute and short-lived psychosis. Our findings would enable early identification of NARP patients and could therefore be of value in developing more specific interventions in this population.