title: Thought disorder index of Finnish adoptees and communication deviance of their adoptive parents.
abstract: BACKGROUND
  Diverse forms of thought disorder, as measured by the Thought Disorder Index (TDI), are found in many conditions other than schizophrenia. Certain thought disorder categories are primarily manifest during psychotic schizophrenic episodes. The present study examined whether forms of thought disorder qualify as trait indicators of vulnerability to schizophrenia in persons who are not clinically ill, and whether these features could be linked to genetic or environmental risk or to genotype-environment interactions. The Finnish Adoptive Study of Schizophrenia provided an opportunity to disentangle these issues.
  
  
  METHODS
  Rorschach records of Finnish adoptees at genetic high risk but without schizophrenia-related clinical diagnoses (N = 56) and control adoptees at low genetic risk (N = 95) were blindly and reliably scored for the Thought Disorder Index (TDI). Communication deviance (CD), a measure of the rearing environment, was independently obtained from the adoptive parents.
  
  
  RESULTS
  The differences in total TDI between high-risk and control adoptees were not statistically significant. However, TDI subscales for Fluid Thinking and Idiosyncratic Verbalization were more frequent in high-risk adoptees. When Rorschach CD of the adoptive rearing parents was introduced as a continuous predictor variable, the odds ratio for the Idiosyncratic Verbalization component of the TDI of the high-risk adoptees was significantly higher than for the control adoptees.
  
  
  CONCLUSIONS
  Specific categories of subsyndromal thought disorder appear to qualify as vulnerability indicators for schizophrenia. Genetic risk and rearing-parent communication patterns significantly interact as a joint effect that differentiates adopted-away offspring of schizophrenic mothers from control adopted-away offspring.
authors.affiliation: Department of Psychiatry, University of Oulu, Finland.
authors.forename: K E
authors.initials: KE
authors.lastname: Wahlberg
authors.forename: L C
authors.initials: LC
authors.lastname: Wynne
authors.forename: H
authors.initials: H
authors.lastname: Oja
authors.forename: P
authors.initials: P
authors.lastname: Keskitalo
authors.forename: H
authors.initials: H
authors.lastname: Anais-Tanner
authors.forename: P
authors.initials: P
authors.lastname: Koistinen
authors.forename: T
authors.initials: T
authors.lastname: Tarvainen
authors.forename: H
authors.initials: H
authors.lastname: Hakko
authors.lastname: Lahti
authors.forename: J
authors.initials: J
authors.lastname: Moring
authors.forename: M
authors.initials: M
authors.lastname: Naarala
authors.forename: A
authors.initials: A
authors.lastname: Sorri
authors.forename: P
authors.initials: P
authors.lastname: Tienari
mesh_terms: D000293:Adolescent; D000300:Adoption; D000328:Adult; D002648:Child; D002668:Child Rearing; D004777:Environment; D005260:Female; D005387:Finland / Q000453:epidemiology; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008606:Mental Processes; D008875:Middle Aged; D010287:Parent-Child Relations; D018570:Risk Assessment; D012559:Schizophrenia / Q000209:etiology / Q000235:genetics*