Olfactory deficits in individuals at risk for psychosis and patients with schizophrenia: relationship with socio-cognitive functions and symptom severity

Odor identification deficits are well documented in patients with schizophrenia, but it remains unclear whether individuals at clinical high-risk for psychosis exhibit similar changes and whether their olfactory function is related to social/cognitive functions and symptomatology. In this study, we investigated odor detection sensitivity and identification ability in 32 individuals with at-risk mental state (ARMS), 59 schizophrenia patients, and 169 healthy controls using a T&T olfactometer. The ARMS and schizophrenia subjects were administered the Brief Assessment of Cognition in Schizophrenia (BACS), the Schizophrenia Cognition Rating Scale (SCoRS), and the Social and Occupational Functioning Assessment Scale (SOFAS) to assess their cognitive and social functions, and the Positive and Negative Syndrome Scale (PANSS) for clinical symptoms. Both the ARMS and schizophrenia subjects had lower odor identification ability when compared with healthy controls, while no significant difference was found in the odor detection sensitivity. The lower odor identification ability in the ARMS group correlated with the severity of negative symptoms and weakly correlated with lower performance on the BACS verbal fluency test. The olfactory measures of schizophrenia patients did not correlate with illness duration, medication, symptom severity, and social and cognitive functions. For the ARMS and schizophrenia groups, the olfactory measures did not correlate with the SOFAS and SCoRS scores. These findings suggest that high-risk subjects for psychosis already show odor identification deficits similar to those observed in schizophrenia patients, which probably reflect a biological trait related to vulnerability to psychosis.