The potential for retronasally delivered olfactory stimuli to assess psychiatric conditions

Abstract

Recent research has linked the ability to identify odours to parts of the brain that, when impaired, are associated with mental illness or disease. The link between impaired odour perception and some psychological disorders has led to the suggestion that standardised assessments probing smell be routinely adopted in the clinical environment. Odour tests currently on the market utilise the orthonasal route, though the retronasal route is a viable, but overlooked, alternative. In this study, a flavour delivery system has been developed which quickly dissolves in the buccal cavity, rapidly releasing flavours that reach the olfactory system by the retronasal route. We tested seven different types of retronasal flavour stimuli (peppermint, aniseed, liquorice, coffee, orange, lemon, and valeric acid) on 171 undergraduate and postgraduate university students and related perceptual measures with psychological wellbeing scores. Olfactory measures included odour identification, pleasantness, intensity, and familiarity. Psychological measures of schizotypy (SPQ-B), depression, stress and anxiety (DASS-21), and autism spectrum disorder (RAADS-R) were obtained to represent psychological wellbeing. A battery of hierarchical multiple linear regressions were run to determine the relationships between odour perception and the psychometric measures. After controlling for age and gender, significant negative associations were found between odour identification and the stress (β = −.347, p < .001), anxiety (β = −.376, p < .001), depression (β = −.318, p < .001), schizotypy (β = −.473, p < .001), and RAADS-R (β = −.285, p < .001) scales. Additionally, both overall pleasantness (β = −.203, p < .01) and intensity (β = .194, p < .05) ratings were negatively correlated to the RAADS-R. Our findings indicate that retronasal stimuli present a feasible alternative to olfactory assessment of psychological states and further reinforces evidence indicating a correlation between olfactory and psychological measures.