title: Exploring the borders of the schizoaffective spectrum: a categorical and dimensional approach.
abstract: BACKGROUND
  Schizoaffective disorder has long been considered as an intermediate condition between major mood disorders and schizophrenia, however, the nature of the relationship to these diagnoses remains unclear. We aimed at examining the nature of such a relationship in a mixed sample of psychotic disorders by using a dimensional and categorical approach to psychopathology.
  
  
  METHODS
  Six-hundred and sixty psychotic inpatients were assessed for lifetime ratings of mania, depression, psychosis and incongruence, diagnosed according to Research Diagnostic Criteria, and classified as having nonaffective psychosis without mood syndromes (n=429), nonaffective psychosis with mood syndromes (n=101), schizoaffective disorder mainly schizophrenic (n=41), schizoaffective disorder mainly affective (n=42) or mood disorder with psychotic symptoms (n=47). We tested for associations of illness-related features including risk factors, premorbid, clinical and outcome variables with classes of disorders and lifetime ratings of psychopathology, and examined the relative contribution of categorical and dimensional representations of psychopathology in explaining disease characteristics.
  
  
  RESULTS
  While categories at the extreme end of the psychotic spectrum meaningfully differed across a number of the illness-related variables, no substantial discontinuity was apparent between adjacent categories of psychotic disorders. Risk factors, premorbid adjustment, clinical features and impairment appeared to be present in a mostly monotonic continuous fashion from nonaffective psychoses to mood disorders with psychotic features. The overall association pattern of illness-related variables with mood and psychotic syndromes was largely independent of specific diagnostic categories, and the dimensional approach was neatly superior to the traditional diagnostic approach in explaining the characteristics of the illness.
  
  
  CONCLUSIONS
  This was a cross-sectional study with retrospective assessment of illness-related-variables and lifetime psychopathology.
  
  
  CONCLUSIONS
  The results are compatible with the notion of the schizoaffective spectrum and with a continuum model of the psychotic illness.
authors.affiliation: Psychiatric Unit, Virgen del Camino Hospital, Pamplona, Spain. victor.peralta.martin@cfnavarra.es
authors.forename: Victor
authors.initials: V
authors.lastname: Peralta
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Cuesta
mesh_terms: D000328:Adult; D017668:Age of Onset; D001714:Bipolar Disorder / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology; D012307:Risk Factors; D012559:Schizophrenia / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D012565:Schizophrenic Psychology; D012917:Social Adjustment; D013030:Spain