THE DIMENSIONAL STRUCTURE OF FIRST EPISODE PSYCHOSIS - AN EXPLORATORYFACTOR-ANALYSIS

Background, Recent research has focused upon the subdiagnostic level i n an effort to derive more valid domains of psychotic disorder. This h as led to the influential positive-negative dichotomy in schizophrenia being superseded by a three-syndrome model. The strategy of looking f or syndromes within poorly validated diagnostic categories, such as sc hizophrenia, has limitations, particularly since it originated in, and has been largely restricted to, the more chronic subsamples. Method. A representative sample of first episode psychosis (N = 509), which in cludes the full spectrum of functional psychosis, was utilized to re-e xamine the dimensional structure of functional psychosis from first pr inciples. Patients were assessed with the Royal Park Multidiagnostic I nstrument for Psychosis (MIP), a comprehensive procedure that document s the psychopathology of the first episode in a clinically valid manne r. Results. Principal axis factor analysis was carried out on the tetr achoric correlation matrix of 92 core psychopathological items. A robu st and clinically valid four-factor solution was obtained, comprising depression, mania and only two other factors. The first was a Bleuleri an blend of negative symptoms, catatonic/motor symptoms and disorganiz ation. The second was a combination of Schneiderian first rank symptom s, and other hallucinations and delusions. The data thus failed to sup port the three-syndrome model for non-affective symptoms in this popul ation. A six-factor solution, although partially consistent with other studies, represented a more complex and confusing elaboration of the more clinically valid four-factor solution. Conclusions. The findings have implications for the conceptualization of early psychosis, which need to be explored further in validation studies.