Characterising psychosis in the Australian National Survey of Mental Health and Wellbeing Study on Low Prevalence (psychotic) Disorders.

OBJECTIVE: This study examines the factorial structure of symptoms and signs in psychosis in data from the Study on Low Prevalence (psychotic) Disorders which is part of the National Survey of Mental Health and Wellbeing, Australia 1997-1998.

METHOD: The present study examined a wide variety of symptoms taken from the Schedules for Clinical Assessment in Neuropsychiatry items and the substance use items in the Diagnostic Interview for Psychosis, an instrument specially constructed for the national study. The instrument was applied to 980 community and hospital subjects with a wide range of psychotic illness diagnoses. The data were factor analysed and scales of 'domains of psychopathology' derived.

RESULTS: The data were best fitted by five principal factors ('domains') which can be approximately labelled dysphoria, positive symptoms, substance use, mania and negative symptoms/incoherence. These factors together explained 55.4% of variance in symptoms. Solutions with more numerous factors did not improve the representation.

CONCLUSION: The five domains successfully characterise a large part of the variance in psychopathology found in the present study of low prevalence (psychotic) disorders. The approach allows sufferer's symptom range and severity to be well expressed without multiple comorbid diagnoses or the limits imposed by categorical diagnosis. Knowledge of alternative dimensional representations of psychopathology may usefully complement our use of categories, enhance awareness of symptoms and ensure that important psychopathology is heeded in practice and research.