title: The structure of psychosis: latent class analysis of probands from the Roscommon Family Study.
abstract: BACKGROUND
  The nosologic structure of psychotic illness, still influenced as much by historical as empirical perspectives, remains controversial.
  
  
  METHODS
  Latent class analysis was applied to detailed symptomatic and outcome assessments of probands (n=343) with broadly defined schizophrenia and affective illness ascertained from a population-based psychiatric registry in Roscommon County, Ireland. First-degree relatives (n=942) were assessed by personal interview and/or review of hospital record.
  
  
  RESULTS
  Six classes were found, all of which bore substantial resemblance to current or historical nosologic constructs. In order of decreasing frequency, they were (1) classic schizophrenia, (2) major depression, (3) schizophreniform disorder, (4) bipolar-schizomania, (5) schizodepression, and (6) hebephrenia. These classes differed on many historical and clinical variables not used in the latent class analysis. Compared with relatives of controls, significantly increased rates of major depression were seen in relatives of depressed and schizodepressed probands. Significantly increased rates of bipolar illness were restricted to relatives of bipolar-schizomanic probands. The risks for schizophrenia and schizophrenia spectrum disorders were significantly increased in relatives of all proband classes except major depression. This increase was moderate for bipolar-schizomanic probands, substantial for schizophrenic, schizophreniform, and schizodepressed probands, and marked for hebephrenic probands.
  
  
  CONCLUSIONS
  These results suggest a relatively complex typology of psychotic syndromes consistent neither with a unitary model nor with a Kraepelinian dichotomy. The familial vulnerability to psychosis extends across several syndromes, being most pronounced in those with schizophrenialike symptoms. The familial vulnerability to depressive and manic affective illness is somewhat more specific.
authors.affiliation: Department of Psychiatry, Medical College of Virginia, Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond 23298-0126, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
authors.forename: L M
authors.initials: LM
authors.lastname: Karkowski
authors.forename: D
authors.initials: D
authors.lastname: Walsh
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001714:Bipolar Disorder / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology; D003866:Depressive Disorder / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology; D005163:Factor Analysis, Statistical; D005190:Family; D005260:Female; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011618:Psychotic Disorders / Q000145:classification* / Q000175:diagnosis* / Q000453:epidemiology; D012042:Registries; D015203:Reproducibility of Results; D012307:Risk Factors; D012559:Schizophrenia / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology; D012562:Schizophrenia, Disorganized / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology