title: Olfactory impairment in monozygotic twins discordant for schizophrenia.
abstract: OBJECTIVE
  Several studies demonstrated olfactory dysfunction in patients with schizophrenia, some reported deficient olfaction in unaffected relatives of schizophrenics as well. This study differentially assessed olfactory acuity as well as smell identification and smell discrimination in monozygotic twins discordant for schizophrenia and healthy, monozygotic control twins, to determine the genetic basis of different olfactory modalities and their association to schizophrenia.
  
  
  METHODS
  The Sniffin'Sticks test,a comprehensive and standardized olfactory test, was employed to assess the olfactory function of 10 monozygotic twin pairs discordant for schizophrenia versus 10 age- and sexmatched healthy,monozygotic twin pairs.
  
  
  RESULTS
  Olfaction of affected monozygotic twins was globally impaired. Partial olfactory impairment of their unaffected co-twins may point to a genetic cause of olfactory impairment in schizophrenia. The influence of genetic factors was most evident for olfactory acuity and least evident for smell identification. All olfactory functions declined with duration of illness. Side of stimulus presentation did not influence olfactory performance.
  
  
  CONCLUSIONS
  Genetic factors associated with olfactory dysfunction may contribute to schizophrenia. The degree of the genetic influence on olfaction depends on the olfactory domain under examination.
authors.affiliation: Klinik für Psychiatrie der Friedrich-Schiller-Universität, Philosophenweg, 07740 Jena, Germany. Tarik.Ugur@med.uni-jena.de
authors.forename: Tarik
authors.initials: T
authors.lastname: Ugur
authors.forename: Matthias
authors.initials: M
authors.lastname: Weisbrod
authors.forename: Ernst
authors.initials: E
authors.lastname: Franzek
authors.forename: Ute
authors.initials: U
authors.lastname: Pfüller
authors.forename: Heinrich
authors.initials: H
authors.lastname: Sauer
mesh_terms: D000328:Adult; D004192:Discrimination, Psychological; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D000857:Olfaction Disorders / Q000235:genetics* / Q000523:psychology; D012559:Schizophrenia / Q000235:genetics*; D012565:Schizophrenic Psychology; D012903:Smell / Q000235:genetics / Q000502:physiology; D014430:Twins, Monozygotic