title: The factor structure and clinical utility of formal thought disorder in first episode psychosis.
abstract: BACKGROUND
  Formal thought disorder (FTD) is a core feature of psychosis, however there are gaps in our knowledge about its prevalence and factor structure. We had two aims: first, to establish the factor structure of FTD; second, to explore the clinical utility of dimensions of FTD in order to further the understanding of its nosology.
  
  
  METHODS
  A cross-validation study was undertaken to establish the factor structure of FTD in first episode psychosis (FEP). The relative utility of FTD categories vs. dimensions across diagnostic categories was investigated.
  
  
  RESULTS
  The prevalence of clinically significant FTD in this FEP sample was 21%, although 41% showed evidence of disorganised speech, 20% displayed verbosity and 24% displayed impoverished speech. A 3-factor model was identified as the best fit for FTD, with disorganisation, poverty and verbosity dimensions (GFI=0.99, RMR=0.07). These dimensions of FTD accurately distinguished affective from non-affective diagnostic categories. A categorical approach to FTD assessment was useful in identifying markers of clinical acuteness, as identified by short duration of untreated psychosis (OR=2.94, P<0.01) and inpatient treatment status (OR=3.98, P<0.01).
  
  
  CONCLUSIONS
  FTD is moderately prevalent and multi-dimensional in FEP. Employing both a dimensional and categorical assessment of FTD gives valuable clinical information, however there may be a need to revise our conceptualisation of the nosology of FTD. The prognostic value of FTD, as well as its neural basis, requires elucidation.
authors.affiliation: Dublin and East Treatment and Early Care Team (DETECT) Service, Blackrock, Co Dublin, Ireland; School of Medicine and Medical Sciences, University College Dublin, Belfield, Dublin, Ireland. Electronic address: eric.roche@sjog.ie.
authors.forename: Eric
authors.initials: E
authors.lastname: Roche
authors.affiliation: Dublin and East Treatment and Early Care Team (DETECT) Service, Blackrock, Co Dublin, Ireland; North Dublin Mental Health Services, Beaumont Hospital, Dublin 9, Ireland. Electronic address: johnlyne@mail.com.
authors.forename: John Paul
authors.initials: JP
authors.lastname: Lyne
authors.affiliation: Dublin and East Treatment and Early Care Team (DETECT) Service, Blackrock, Co Dublin, Ireland; School of Medicine and Medical Sciences, University College Dublin, Belfield, Dublin, Ireland; Orygen, The National Centre of Excellence in Youth Mental Health, Melbourne, Australia. Electronic address: briannoelodonoghue@gmail.com.
authors.forename: Brian
authors.initials: B
authors.lastname: O'Donoghue
authors.affiliation: UCD CSTAR, School of Public Health, Physiotherapy and Population Science, University College Dublin, Belfield, Dublin, Ireland. Electronic address: ricardo.segurado@ucd.ie.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Segurado
authors.affiliation: Dublin and East Treatment and Early Care Team (DETECT) Service, Blackrock, Co Dublin, Ireland. Electronic address: akinsella@rcsi.ie.
authors.forename: Anthony
authors.initials: A
authors.lastname: Kinsella
authors.affiliation: Graduate Entry Medical School, University of Limerick, Limerick, Ireland. Electronic address: ailish.hannigan@ul.ie.
authors.forename: Ailish
authors.initials: A
authors.lastname: Hannigan
authors.affiliation: School of Medicine and Medical Sciences, University College Dublin, Belfield, Dublin, Ireland; Mater Misericordiae University Hospital, Dublin, Ireland. Electronic address: brendankelly35@gmail.com.
authors.forename: Brendan D
authors.initials: BD
authors.lastname: Kelly
authors.affiliation: School of Medicine and Medical Sciences, University College Dublin, Belfield, Dublin, Ireland; St Vincent's University Hospital, Dublin, Ireland. Electronic address: k.malone@svuh.ie.
authors.forename: Kevin
authors.initials: K
authors.lastname: Malone
authors.affiliation: Dublin and East Treatment and Early Care Team (DETECT) Service, Blackrock, Co Dublin, Ireland; School of Medicine and Medical Sciences, University College Dublin, Belfield, Dublin, Ireland. Electronic address: mary.clarke@sjog.ie.
authors.forename: Mary
authors.initials: M
authors.lastname: Clarke
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003072:Cognition Disorders / Q000453:epidemiology* / Q000209:etiology*; D003147:Communication Disorders / Q000453:epidemiology* / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D025341:Principal Component Analysis; D011618:Psychotic Disorders / Q000150:complications*; D012189:Retrospective Studies; D013850:Thinking / Q000502:physiology*; D055815:Young Adult
keywords: Clinical utility; Factor structure; Language; Prevalence; Psychosis; Thought disorder