title: Definition and prevalence of severe and persistent mental illness.
abstract: BACKGROUND
  There is little consistency in how severe mental illness (SMI) is defined in practice, and no operational definitions.
  
  
  OBJECTIVE
  To test two operationalized definitions, based on the National Institute of Mental Health (1987) definition: the first uses three criteria (diagnosis of psychosis; duration of service contact > or = 2 years; GAF score < or = 50), the second only the last two.
  
  
  METHODS
  Annual prevalence rates of SMI in two European catchment areas for each criterion and the criteria combined were calculated.
  
  
  RESULTS
  The first definition produced rates of 2.55 and 1.34/1000 in London and Verona, respectively; the second permitted an additional 0.98/1000 non-psychotic disorders to be included in Verona.
  
  
  CONCLUSIONS
  The three-dimensional definition selects a small group of patients with SMI who have psychotic disorders. The two-dimensional approach allows estimates of SMI prevalence rates which include all forms of mental disorder.
authors.affiliation: Dipartimento di Medicina e Sanità Pubblica, Università di Verona, Ospedale Policlinico, Italy. mruggeri@borgoroma.univr.it
authors.forename: M
authors.initials: M
authors.lastname: Ruggeri
authors.forename: M
authors.initials: M
authors.lastname: Leese
authors.forename: G
authors.initials: G
authors.lastname: Thornicroft
authors.forename: G
authors.initials: G
authors.lastname: Bisoffi
authors.forename: M
authors.initials: M
authors.lastname: Tansella
mesh_terms: D000328:Adult; D002908:Chronic Disease; D003431:Cross-Cultural Comparison; D003710:Demography; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008131:London / Q000453:epidemiology; D008297:Male; D008605:Mental Health Services / Q000706:statistics & numerical data; D008875:Middle Aged; D011618:Psychotic Disorders / Q000145:classification / Q000453:epidemiology*; D012959:Socioeconomic Factors; D009626:Terminology as Topic