Various bilateral olfactory deficits in male patients with schizophrenia

Olfactory identification deficits in schizophrenia patients are well documented. Less is known about the functioning of other olfactory domains and the possibility of lateralized dysfunctions. Thirty male schizophrenia patients and 30 male healthy controls underwent unirhinal assessment of various olfactory domains: detection threshold (dimethyl disulfide, phenyl ethanol), quality discrimination, and odor ratings (familiarity, pleasantness, edibility, intensity) of pure chemicals (Munich Olfaction Test), as well as familiarity and edibility judgments and identification of everyday odors. Aside from impaired identification, patients showed impaired familiarity and edibility judgments of everyday odors. With regard to odor ratings of pure chemicals, group differences were observed only in pleasantness ratings, with higher ratings in patients. Furthermore, patients had reduced sensitivity with dimethyl disulfide and reduced quality discrimination compared with controls. Further analyses showed that identification deficits were not attributable to reduced sensitivity but may be associated with impairments in quality discrimination. Olfactory dysfunctions were found across both nostrils. Results suggest specific dysfunctions in olfactory processing in schizophrenia patients, including early stages of the odor identification process.