title: Familial clustering of schizophrenia, bipolar disorder, and major depressive disorder.
abstract: OBJECTIVE
  To investigate familial clustering of schizophrenia, bipolar disorder, and major depressive disorder.
  
  
  METHODS
  Combining data from a psychiatric case registry and Statistics Netherlands provided information on 4,673 affected probands and 18,692 matched population controls.
  
  
  RESULTS
  Probands with schizophrenia had relative risks (RRs) for having a sibling with schizophrenia of 3.77 (95% confidence interval (CI): 2.60-5.46) and with bipolar disorder of 1.79 (95% CI: 0.64-4.96) as compared with a reference proband. Probands affected with bipolar disorder have an RR of 6.51 (95% CI: 2.60-16.29) for having a sibling with bipolar disorder and of 1.71 (95% CI: 0.71-4.14) for having a sibling with schizophrenia as compared with a reference proband. Probands affected with major depressive disorder also have increased risk for having a sibling with schizophrenia (RR: 2.04, 95% CI: 1.54-2.72) as compared with a reference proband, which was similar to the risk for having a sibling with major depressive disorder (RR: 1.91, 95% CI: 1.63-2.24) or bipolar disorder (RR: 2.06, 95% CI: 1.18-3.60).
  
  
  CONCLUSIONS
  Our findings suggest, as previous studies have, that risk across schizophrenia and bipolar disorder is considerably lower (twofold) than within diagnostic entities, whereas for major depressive disorder risk is similar within and across diagnostic entities.
authors.affiliation: Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center Utrecht, Utrecht, The Netherlands. M.Aukes@umcutrecht.nl
authors.forename: Maartje F
authors.initials: MF
authors.lastname: Aukes
authors.forename: Wijnand
authors.initials: W
authors.lastname: Laan
authors.forename: Fabian
authors.initials: F
authors.lastname: Termorshuizen
authors.forename: Jacobine E
authors.initials: JE
authors.lastname: Buizer-Voskamp
authors.forename: Eric A M
authors.initials: EA
authors.lastname: Hennekam
authors.forename: Hugo M
authors.initials: HM
authors.lastname: Smeets
authors.forename: Roel A
authors.initials: RA
authors.lastname: Ophoff
authors.forename: Marco P M
authors.initials: MP
authors.lastname: Boks
authors.forename: René S
authors.initials: RS
authors.lastname: Kahn
mesh_terms: D000328:Adult; D000367:Age Factors; D001714:Bipolar Disorder / Q000453:epidemiology*; D016000:Cluster Analysis; D003865:Major Depressive Disorder / Q000453:epidemiology*; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D012306:Risk; D012559:Schizophrenia / Q000453:epidemiology*; D012737:Sex Factors; D055815:Young Adult