title: Psychosis among "healthy" siblings of schizophrenia patients.
abstract: BACKGROUND
  Schizophrenia aggregates in families and accurate diagnoses are essential for genetic studies of schizophrenia. In this study, we investigated whether siblings of patients with schizophrenia can be identified as free of any psychotic disorder using only register information. We also analyzed the emergence of psychotic disorders among siblings of patients with schizophrenia during seven to eleven years of follow-up.
  
  
  METHODS
  A genetically homogenous population isolate in north-eastern Finland having 365 families with 446 patients with a diagnosis of schizophrenia was initially identified in 1991 using four nationwide registers. Between 1998 and 2002, 124 patients and 183 siblings in 110 families were contacted and interviewed using SCID-I, SCID-II and SANS. We also compared the frequency of mental disorders between siblings and a random population comparison group sample.
  
  
  RESULTS
  Thirty (16%) siblings received a diagnosis of psychotic disorder in the interview. 14 siblings had had psychotic symptoms already before 1991, while 16 developed psychotic symptoms during the follow-up. Over half of the siblings (n = 99, 54%) had a lifetime diagnosis of any mental disorder in the interview.
  
  
  CONCLUSIONS
  Register information cannot be used to exclude psychotic disorders among siblings of patients with schizophrenia. The high rate of emergence of new psychotic disorders among initially healthy siblings should be taken into account in genetic analysis.
authors.affiliation: Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland. ritva.arajarvi@ktl.fi
authors.forename: Ritva
authors.initials: R
authors.lastname: Arajärvi
authors.forename: Jonna
authors.initials: J
authors.lastname: Ukkola
authors.forename: Jari
authors.initials: J
authors.lastname: Haukka
authors.forename: Jaana
authors.initials: J
authors.lastname: Suvisaari
authors.forename: Jukka
authors.initials: J
authors.lastname: Hintikka
authors.forename: Timo
authors.initials: T
authors.lastname: Partonen
authors.forename: Jouko
authors.initials: J
authors.lastname: Lönnqvist
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics; D008875:Middle Aged; D015995:Prevalence; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D011618:Psychotic Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics; D012042:Registries / Q000706:statistics & numerical data; D012107:Research Design; D012307:Risk Factors; D012494:Sampling Studies; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics*; D012565:Schizophrenic Psychology; D035781:Siblings / Q000523:psychology*