title: Do symptom dimensions or categorical diagnoses best discriminate between known risk factors for psychosis?
abstract: OBJECTIVE
  To describe symptom dimensions of psychosis using detailed psychopathological information from epidemiologically defined incident cases which include the full spectrum of functional psychosis across all age ranges. Then, assess the comparative usefulness of the dimensional and categorical representations of psychosis in discriminating between demographic and pre-morbid risk factors.
  
  
  METHODS
  A total of 464 incident cases of psychosis assessed with OPCRIT (Operational Checklist for Psychotic Symptoms) were included in an exploratory factor analysis. Using Regression analyses we modelled the associations of the dimensional and categorical representations of psychosis with antecedent validating variables and compared the subsequent models using the likelihood ratio test.
  
  
  RESULTS
  Factor analysis produced five-symptom dimensions, manic, disorganisation, depressive, delusional and auditory hallucinatory symptoms, explaining 58% of the total variance. Different dimensions were differentially associated with the pre-morbid risk factors. Neither the dimensional nor the categorical representations on their own were sufficient to explain associations with the antecedent validating variables.
  
  
  CONCLUSIONS
  Neither the dimensional or the diagnostic representation of psychosis was superior in discriminating between known risk factors, combining dimensional measures with categorical diagnoses will probably be more informative in determining the causes and correlates of psychosis.
authors.affiliation: Dept. of Psychiatry and Neuropsychology, Maastricht University, P.O. Box 616 (location DOT10), 6200 MD Maastricht, The Netherlands. j.allardyce@clinmed.gla.ac.uk
authors.forename: Judith
authors.initials: J
authors.lastname: Allardyce
authors.forename: Robin G
authors.initials: RG
authors.lastname: McCreadie
authors.forename: Gary
authors.initials: G
authors.lastname: Morrison
authors.forename: Jim
authors.initials: J
authors.lastname: van Os
mesh_terms: D000328:Adult; D017668:Age of Onset; D001526:Behavioral Symptoms / Q000145:classification / Q000175:diagnosis*; D003156:Community Mental Health Services / Q000706:statistics & numerical data; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D011237:Predictive Value of Tests; D011569:Psychiatric Status Rating Scales / Q000592:standards*; D011618:Psychotic Disorders / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D012044:Regression Analysis; D015203:Reproducibility of Results; D012307:Risk Factors; D012606:Scotland / Q000453:epidemiology; D017678:Sex Distribution