The hierarchical organization of symptom dimensions in first episode psychosis and the relationship to diagnostic classification

Manuela Russo, STEPHEN LEVINE, Arsime Demjaha, Marta Di Forti, V Mondelli, M Belvederi-Murri, B Wiffen, Paola Dazzan, Paul Fearon, Craig Morgan, Robin M. Murray, Abraham Reichenberg

Research output: Contribution to conferencePoster


Background: The categorical approach to psychosis is under increasing criticism due to its inability to explain the heterogeneity of psychotic disorders.
A multi-dimensional approach may be a useful supplement to discrete nosological entities for clinicians and research workers. There is, however, no definitive dimensional model to describe psychosis. This study aims to examine the organization of symptom severity in early psychosis and to determine
the interchangeability of categorical and dimensional approaches to psychosis. Methods: First episode psychosis patients participating in an epidemiological study (n = 500) were included. Symptom severity was assessed using the Schedule for Clinical Assessment in Neuropsychiatry (SCAN) and rated through the SCAN’s Item Group Checklist (IGC). To assess the organization
of symptoms Principal Component Analysis with oblique rotation (Promax) was used. Schimd-Leiman solution was applied to explain direct and indirect relationships between lower and higher order factors. Concordance between categorical diagnosis and the dimensional model was evaluated with Recursive Partitioning and Multinomial Logistic Regression modelling. Results: Using a parallel scree plot, a first order six-factor model was identified
that accounted for 63% of the variance and best fitted the data. The factors that emerged were: Mania, Negative, Disorganization, Depression, Hallucinations and Delusions. Higher order factor analysis was performed on the first order factors and gave rise to two second order factors accounting for 49.5% of variance and discriminating the affective (Disorganization/Mania/ Depression) from the non-affective (Hallucinations/Negative/Delusions)
characteristics of psychosis. Concordance rate between categorical and dimensional classification methods was 74%. Conclusion: Findings are consistent with a hierarchical organization of psychosis characterized by 6 symptoms dimensions that split into 2 higher-order factors discriminating
affective from non affective psychosis. The dimensional model showed an overall good agreement with the traditional diagnostic categories.
ID: 979114
Original languageEnglish
Number of pages1
StatePublished - 2011
EventThe 13th International Congress on Schizophrenia Research - Colorado Springs, United States
Duration: 1 Jan 20111 Jan 2011


ConferenceThe 13th International Congress on Schizophrenia Research
Country/TerritoryUnited States
CityColorado Springs


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