Olfactory functioning in schizophrenia: relationship to clinical, neuropsychological, and volumetric MRI measures

Deficits in odor identification and detection threshold sensitivity have been observed in schizophrenia but their relationship to clinical, cognitive, and biologic measures have not been clearly established. Our objectives were to examine the relationship between measures of odor identification and detection threshold sensitivity and clinical, neuropsychological, and anatomic brain measures. Twenty-one patients with schizophrenia and 20 healthy controls were administered psychophysical tests of odor identification and detection threshold sensitivity to phenyl ethyl alcohol. In addition, clinical symptom ratings, neuropsychological measures of frontal and temporal lobe function and whole brain MRIs were concurrently obtained. Patients exhibited significant deficits in odor identification but normal detection threshold sensitivity. Poorer odor identification scores were associated with longer duration of illness, increased negative and disorganized symptoms, and the deficit syndrome, as well as impairments in verbal and nonverbal memory. Better odor detection thresholds were specifically associated with first-rank or productive symptoms. Larger left temporal lobe volumes with MRI were associated with better odor identification in controls but not in patients. Given the relevance of the neural substrate, and the evidence of performance deficits, psychophysical probes of the integrity of the olfactory system hold special promise for illuminating aspects of the neurobiology underlying schizophrenia.