title: Do schizotypal symptoms mediate the relationship between genetic risk for schizophrenia and impaired neuropsychological performance in co-twins of schizophrenic patients?
abstract: BACKGROUND
  Neurocognitive deficits and symptoms of schizotypal personality disorder are both elevated in the first-degree relatives of schizophrenic patients, but their relationship to each other and their potential common genetic source remain unclear.
  
  
  METHODS
  Fifty unaffected co-twins of schizophrenic patients and 123 control twins were assessed with a neuropsychological battery and structured clinical interviews.
  
  
  RESULTS
  Working memory was influenced by genetic risk for schizophrenia but not schizotypal symptoms. Nearly all other domains were influenced by schizotypy symptoms but only in the co-twins of schizophrenic patients. Schizotypy symptoms in the absence of a family history did not seem to be related to impaired neurocognitive functioning.
  
  
  CONCLUSIONS
  Schizotypy symptoms in those with genetic risk for schizophrenia are associated with increased risk for cognitive deficits. Some neurocognitive deficits might covary with subpsychotic symptoms due to a shared genetic factor. Community-ascertained schizotypal individuals might not be appropriate for modeling underlying genetic risk for schizophrenia.
authors.affiliation: Department of Psychology (JKJ), University of California at Los Angeles, Los Angeles, California California 90095-1563, USA.
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Johnson
authors.forename: Annamari
authors.initials: A
authors.lastname: Tuulio-Henriksson
authors.forename: Tiia
authors.initials: T
authors.lastname: Pirkola
authors.forename: Matti O
authors.initials: MO
authors.lastname: Huttunen
authors.forename: Jouko
authors.initials: J
authors.lastname: Lönnqvist
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Tyrone D
authors.initials: TD
authors.lastname: Cannon
mesh_terms: D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D012565:Schizophrenic Psychology; D012569:Schizotypal Personality Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D012917:Social Adjustment; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic