Objective and Subjective Olfaction Across the Schizophrenia Spectrum

Abstract

Much research indicates that patients with schizophrenia have impaired olfaction detection ability. However, studies of individuals with psychometrically defined schizotypy reveal mixed results-some document impairments while others do not. In addition to deficits in objective accuracy in olfaction for patients with schizophrenia, there has been an interest in subjective experience of olfaction. Unfortunately, methods of assessing accuracy and subjective hedonic olfactory evaluations in prior studies may not have been sensitive enough to detect group differences in this area. This study employed a measure of olfactory functioning featuring an expanded scoring system to assess both accuracy and subjective evaluations of pleasant and unpleasant experience. Data were collected for patients with schizophrenia, young adults with psychometrically defined schizotypy, psychiatric outpatients, and healthy controls. Results of this study indicate that both the schizophrenia and outpatient psychiatric groups showed similar levels of impaired olfaction ability; however, the schizotypy group was not impaired in olfaction detection. Interestingly, with regard to subjective hedonic evaluation, it was found that patients with schizophrenia did not differ from psychiatric outpatients, whereas individuals with schizotypy tended to rate smells as significantly less pleasant than healthy control participants. This suggests that subjective olfactory assessment is abnormal in some manner in schizotypy. It also suggests that accuracy of olfaction identification may be a characteristic of severe mental illness across severe mental illness diagnoses. The results are potentially important for understanding olfaction deficits across the mental illness spectrum.

The paradox of schizotypy: Resemblance to prolonged severe mental illness in subjective but not objective quality of life

“…The notion that satisfaction reflects a stable “set point” that is, in large part, heritable (Lykken and Tellegen, 1996) is interesting in that schizotypal features are largely stable (Chapman et al, 1994) and, at least to some degree, heritable (Docherty and Sponheim, 2008; MacDonald et al, 2001). In this regard, subjective dissatisfaction, whether it be in QOL, cognitive concerns (Chun et al, In Press) or in response to laboratory stimuli (Auster et al, 2013; Cohen et al, 2012a), may reflect stable trait features, and perhaps more importantly, a marker of illness vulnerability.…”

“…Thus, there appears to be discrepancy between subjective and objective emotion functioning in college schizotypy. Third, a dysjunction has been reported in olfactory functions (Auster et al, 2013). In this study, college individuals with schizotypy reported lower levels of subjective pleasure when rating a range of olfaction stimuli compared to both patients with schizophrenia and college controls.…”

“…An interesting paradox regarding these individuals has been revealed in the literature recently (e.g., Auster et al, 2013; Chun et al, In Press; Cohen et al, 2012a). The paradox in question concerns how individuals with self-reported schizotypy, particularly those recruited from relatively demanding universities (and are thus presumably demonstrating academic, social and cognitive functioning that is not demonstrably impaired), resemble outpatients in key self-reported variables.…”

Olfaction, among the First Senses to Develop and Decline

“…Moreover, the negative symptoms which characterize this illness have been related to the dysfunction in olfactory accuracy [193]. Nevertheless, there are controversial reports describing an alteration in the sense of smell in schizophreniaassociated disorders [190,194] and others showing the absence of olfactory changes between psychotic patients and healthy controls [193,195,196]. Starting from this discrepancy, Auster and colleagues addressed whether the presence of olfactory deficits could represent a reliable marker for subjects potentially susceptible to develop schizophrenia.…”

“…Starting from this discrepancy, Auster and colleagues addressed whether the presence of olfactory deficits could represent a reliable marker for subjects potentially susceptible to develop schizophrenia. They investigated this aspect comparing the smell functionality in four different groups: (1) schizophrenic individuals, (2) persons with different mental disorders than schizophrenia, (3) subjects affected by schizotypy and (4) healthy controls [193]. To achieve their goal, they modified a common olfaction test, the "Sniffin' Sticks" [193,197], in order to expand its efficiency for free recall tests in addition to olfaction ability and discrimination.…”