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.

The effect of odor valence on olfactory performance in schizophrenia patients, unaffected relatives and at-risk youth

“…Participants provided written informed consent following a full explanation of the study procedures. Data from these subjects were included in a previous publication (Kamath, Turetsky et al, 2011b). …”

“…CR subjects were either unmedicated ( n = 12), taking atypical antipsychotic medication ( n = 1), taking a stimulant medication ( n = 1), or taking other psychotropic medications at the time of testing ( n = 1). With the exception of 5 CR subjects, data from these subjects were included in a previous publication (Kamath, et al, 2011b). …”

Neurology Issues in Schizophrenia

“…Several original articles on the topic have been published in the past years, e.g., [19][20][21][22]. By examining patients with schizophrenia (n=65), first-degree relatives (n=24) as well as youths at clinical (n=10) or genetic risk (n=14) for schizophrenia, isolated deficits in odor identification were identified as genetic markers of vulnerability for schizophrenia, while odor discrimination deficits were proposed as possible biomarkers associated with the development of overt schizophrenia [23]. However, findings on smell identification in individuals at clinical high risk for schizophrenia are inconclusive, and a recent study did not find any utility of two smell identification tasks in predicting emergent schizophrenia [24].…”

Olfactory identification deficits at identification as ultra-high risk for psychosis are associated with poor functional outcome

“…They are also present in first-degree relatives (Kamath et al, 2014;Keshavan et al, 2009;Kopala et al, 1998;Moberg et al, 2013;Roalf et al, 2006) and people with schizotypal features, although to a lesser extent (Moberg et al, 2013), suggesting that they are a possible endophenotype for the disorder. This would imply that OI deficits are detectable in at-risk populations before the onset of frank psychotic illness.…”

“…This would imply that OI deficits are detectable in at-risk populations before the onset of frank psychotic illness. Indeed there is evidence that young people clinically at ultrahigh risk (UHR) for psychosis also show impaired OI (Brewer et al, 2003;Kamath et al, 2014Kamath et al, , 2012Woodberry et al, 2010), with a pooled medium to large effect size (Moberg et al, 2013;Turetsky et al, 2012). Moreover, OI deficits may be a marker of transition from the UHR state to schizophrenia specifically (rather than "psychosis" more generally) (Brewer et al, 2003).…”