title: Phenotypic variation between parent-offspring trios and non-trios in genetic studies of schizophrenia.
abstract: BACKGROUND
  Phenotypic differences between parent-offspring trios and non-trios have been reported for various psychiatric disorders, and it has been suggested that this may make comparisons of case-control and family-based results for gene-disease association studies inappropriate.
  
  
  OBJECTIVE
  To compare phenotypes between trios and non-trios with schizophrenia, and explore possible reasons for differences observed.
  
  
  METHODS
  Phenotypes were compared between trios (n=75) and non-trios (n=424) collected as part of a case-control study.
  
  
  RESULTS
  Differences were observed for most phenotypes investigated, although all were eliminated after adjusting for confounding.
  
  
  CONCLUSIONS
  Confounding, genetic heterogeneity or selection bias could result in differences in case-control and family-based results. However as we discuss, where adequately designed case-control studies are used, gene-disease association results would be incomparable between family-based and case-control studies only if genetic heterogeneity was present. These results do not support the presence of such genetic heterogeneity in schizophrenia.
authors.affiliation: Department of Psychological Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK. zammits@cardiff.ac.uk
authors.forename: Stanley
authors.initials: S
authors.lastname: Zammit
authors.forename: Glyn
authors.initials: G
authors.lastname: Lewis
authors.forename: Anita
authors.initials: A
authors.lastname: Thapar
authors.forename: Richard
authors.initials: R
authors.lastname: Owen
authors.forename: Gaynor
authors.initials: G
authors.lastname: Jones
authors.forename: Susan
authors.initials: S
authors.lastname: Jones
authors.forename: Rob
authors.initials: R
authors.lastname: Sanders
authors.forename: Charis
authors.initials: C
authors.lastname: Milham
authors.forename: Ameera
authors.initials: A
authors.lastname: Mahdi
authors.forename: Michael C
authors.initials: MC
authors.lastname: O'Donovan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Owen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors; D012559:Schizophrenia / Q000175:diagnosis / Q000235:genetics*