title: Incidence of schizophrenia in Nottingham. A comparison of two cohorts, 1978-80 and 1992-94.
abstract: BACKGROUND
  Several studies have reported a decline of up to 50% in the incidence of schizophrenia over recent decades. We aimed to measure changes in the incidence and diagnostic patterns of first-episode psychosis by comparing two Nottingham cohorts, identified in two equal periods separated by 14 years.
  
  
  METHODS
  Two prospectively ascertained cohorts of first-episode psychotic disorder were identified over the time periods 1978-80 and 1992-94. The earlier cohort was of the World Health Organization Determinants of Outcome of Severe Mental Disorder (DOSMD) ten-country study. The later cohort was obtained using similar methodology. Both groups were diagnosed using ICD-10 diagnostic criteria and age-standardised incidence rates were compared.
  
  
  RESULTS
  The standardised incidence rate for all psychotic disorders rose slightly from 2.49 to 2.87 per 10000 population per year, but the F20 classification fell significantly by over a third (1.41 to 0.87 per 10000 per year). The second study group (1992-1994) included a greater diversity of psychotic diagnoses compared with the first, in particular an increased proportion of acute and drug-related psychoses.
  
  
  CONCLUSIONS
  Methodological considerations call for caution in interpreting such data, but we conclude that the significant fall in the narrowly defined diagnostic category of schizophrenia reflects a real change in the syndromal presentation of psychotic disorders.
authors.affiliation: Department of Psychiatry, University of Nottingham.
authors.forename: J
authors.initials: J
authors.lastname: Brewin
authors.forename: R
authors.initials: R
authors.lastname: Cantwell
authors.forename: T
authors.initials: T
authors.lastname: Dalkin
authors.forename: R
authors.initials: R
authors.lastname: Fox
authors.forename: I
authors.initials: I
authors.lastname: Medley
authors.forename: C
authors.initials: C
authors.lastname: Glazebrook
authors.forename: R
authors.initials: R
authors.lastname: Kwiecinski
authors.forename: G
authors.initials: G
authors.lastname: Harrison
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012559:Schizophrenia / Q000453:epidemiology*