title: A preliminary investigation of olfactory function in olfactory and auditory-verbal hallucinators with schizophrenia, and normal controls.
abstract: BACKGROUND
  It is well established that people with schizophrenia have impaired olfactory perception. However, another olfactory abnormality that occurs in schizophrenia--olfactory hallucinations (OHs)--has received almost no attention.
  
  
  METHODS
  This preliminary study compared a small sample of olfactory (OH; n=14) and auditory-verbal (AVH; n=11) hallucinators with schizophrenia, with matched healthy controls (NC; n=21), on tests of odour detection threshold, identification, and hedonics, and bespoke tests relating to possible causes of OHs.
  
  
  RESULTS
  Both OH and AVH participants were equally impaired on tests of odour identification, but neither had any impairment in detection. However, although the AVH group had hedonic impairments, these were not evident in the OH and NC groups. Examination of the possible causes of OHs revealed abnormalities in olfactory habituation. In addition, we observed a far greater rate of past episodes of brief unconsciousness in the OH group.
  
  
  CONCLUSIONS
  The presence of habituation deficits and past episodes of brief unconsciousness, and absence of olfactory affective impairment, have not been identified before as correlates of OHs, suggesting these factors may be worthy of further investigation.
authors.affiliation: Department of Psychology, Macquarie University, Australia. dick.stevenson@mq.edu.au
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Stevenson
authors.forename: Robyn
authors.initials: R
authors.lastname: Langdon
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006185:Habituation, Psychophysiologic; D006212:Hallucinations / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D055696:Olfactory Perception; D010468:Perceptual Disorders / Q000503:physiopathology; D012559:Schizophrenia / Q000503:physiopathology*