Olfactory processing in schizophrenia, non-ill first-degree family members, and young people at-risk for psychosis

Abstract

Objectives. While deficits in odor identification and discrimination have been reported in schizophrenia, few studies have examined the relative specificity of these deficits in patients and at-risk youth. Method. Sniffin’ Sticks odor identification and discrimination were assessed in schizophrenia outpatients and non-ill first-degree relatives (Study One), as well as youth at clinical (CR) or genetic (GR) risk for schizophrenia (Study Two). Scores were z-transformed, using the performance of a demographically-matched adult or adolescent comparison group. Results. Patients and relatives were impaired on odor identification, but odor discrimination impairment was limited to the patient group. A similar pattern of impairment emerged in at-risk youth. GR youth were impaired on odor identification but not discrimination, while CR youth were impaired on both tasks. In patients, olfactory impairment was correlated with negative symptomatology. Conclusions. To our knowledge, this is the first study to show that CR youth are impaired on both olfactory tasks, as observed in adult schizophrenia patients. GR youth were impaired only on odor identification like their adult counterparts. These data suggest that odor identification impairment, in isolation, may represent a genetic marker of vulnerability for schizophrenia, while odor discrimination deficits may be a biomarker associated with the development of psychosis.

Key words::

• Olfaction
• smell
• prodrome
• negative symptoms
• psychosis prone

Acknowledgements

We wish to thank Dana Marchetto, BA, and Jared Hammond, BA, for assistance with subject recruitment, task administration and data entry, Larry Macy, PhD, and Lan Gao, MS, for assistance with data management, as well as the Hofmann Trust for their support of this research through the Brain and Behavior Research Foundation (formerly NARSAD, the National Alliance for Research on Schizophrenia and Depression).

Statement of interest

VK, MEC, CGK, PJM, KBM, DEG, and CGC report no competing interests. BIT and REG report investigator-initiated research support from AstraZeneca Pharmaceuticals and Pfizer Inc. This study was funded by National Institutes of Health Grants MH63381 to Dr Moberg, MH59852 to Dr Turetsky, K08MH79364 to Dr Calkins, K23MH079498 to Dr Borgmann-Winter, MH66121 to Dr Gur, Independent Investigator Awards from NARSAD to Dr Moberg and Dr Borgmann-Winter, and unrestricted funds from the Children's Hospital of Philadelphia to Dr Borgmann-Winter.