title: Heritability of Schneider's first-rank symptoms.
abstract: BACKGROUND
  Schneider's first-rank symptoms are given particular weight when making a diagnosis of schizophrenia, but the nuclear syndrome, characterised by one or more first-rank symptoms, has been found previously to have no heritability.
  
  
  OBJECTIVE
  To estimate the heritability of the nuclear syndrome.
  
  
  METHODS
  A total of 224 twin pairs (106 monozygotic, 118 same-gender dizygotic) were ascertained from the Maudsley Twin Register in London via probands with any psychosis. Lifetime-ever first-rank symptoms were rated using the OPCRIT checklist. Probandwise concordance rates were calculated for the nuclear syndrome and a heritability estimate was derived from biometric model fitting.
  
  
  RESULTS
  Probandwise concordance rates were 13/49 (26.5%) for monozygotic and 0/45 to 2/46 (0.0-4.3%) for dizygotic pairs. The heritability estimate for the best-fitting model was 71% (95% CI 57-82).
  
  
  CONCLUSIONS
  These results indicate that the nuclear syndrome shows substantial heritability, although this is slightly lower than that for schizophrenia as defined by the DSM and ICD systems.
authors.affiliation: Department of Psychological Medicine, University of Wales College of Medicine, Cardiff, Wales, UK.
authors.forename: Alastair G
authors.initials: AG
authors.lastname: Cardno
authors.forename: Pak C
authors.initials: PC
authors.lastname: Sham
authors.forename: Anne E
authors.initials: AE
authors.lastname: Farmer
authors.forename: Robin M
authors.initials: RM
authors.lastname: Murray
authors.forename: Peter
authors.initials: P
authors.lastname: McGuffin
mesh_terms: D000328:Adult; D001699:Biometry; D004200:Diseases in Twins / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000175:diagnosis / Q000235:genetics*; D013577:Syndrome; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic