Clinical correlates of olfactory hallucinations in schizophrenia

Abstract

OBJECTIVES. Olfactory hallucinations (OHs) are underrepresented in conventional clinical instruments, infrequently researched, and poorly understood. To advance understanding of OHs, we examined their past-month prevalence and co-occurring symptoms in two datasets. DESIGN. One dataset comprised categorical codes and was examined using homogeneity analysis and logistic regression; the other dataset comprised numeric ratings and was examined using principal components analyses and linear regression. METHOD. The two datasets included: (1) 962 cases with Present State Examination - 9th Edition (PSE-9), codes (recoded present/absent) from the World Health Organization 10 Country (WHO-10) Study and (2) 265 cases with ratings on Scales for Assessing Positive/Negative Symptoms of Schizophrenia (SAPS/SANS). Two PSE-9 items (external- and self-smells) were recoded into a single OH item to examine consistency with the SAPS/SANS dataset, which contained a single OH item. RESULTS. Prevalence of OHs and hallucinations in other modalities differed according to the WHO-10 international centre. Across centres, OHs were present in 13% of the WHO-10 dataset, similar to the 17% prevalence rate in the SAPS/SANS dataset. Referential/control delusions and other hallucinations (particularly, somatic/tactile/gustatory hallucinations) were significant independent correlates of OHs in both datasets. OHs also co-occurred with social anxiety and depression in the WHO-10 dataset, with self-smells being particularly associated with self-depreciation. CONCLUSIONS. Sociocultural factors may modulate the self-reporting and/or detection of OHs and hallucinations in other modalities. Referential/control delusions promote the generation and/or maintenance of OHs independent of factors shared with other hallucinations. OHs and hallucinations of taste, touch, and bodily sensation frequently co-occur. Self-smells warrant sensitive probing.

Twenty year multi-follow-up of different types of hallucinations in schizophrenia, schizoaffective disorder, bipolar disorder, and depression

“…This suggests olfactory hallucinations are largely a phenomenon that occurs in schizophrenia patients, and to a lesser degree in schizoaffective and bipolar patients. Similar to our findings, olfactory hallucinations were present in 13% of schizophrenia patients in the World Health Organization 10 County dataset, consisting of approximately 1000 patients (Langdon et al, 2011). Other studies have found rates of olfactory hallucinations ranging from 7% to 35% of their schizophreniaspectrum samples (reviewed in Langdon et al, 2011).…”

Perceptual abnormalities in clinical high risk youth and the role of trauma, cannabis use and anxiety

“…In the visual modality, complex perceptual abnormalities typically take the shape of a person, a face, an animal, a landscape or a scene, while simple perceptual abnormalities may take the form of flashes, shapes, geometric patterns, or shadows (Blom, 2010; Ffytche and Wible, 2014). Despite the documentation of the diversity of hallucinatory experiences, current research on hallucinations in psychiatric populations has mainly focused on auditory verbal hallucinations while hallucinations in other modalities or subtypes of hallucinations are less well understood (Langdon et al, 2011; Waters et al, 2014). …”

An Integrative Bayesian Modeling Approach to Imaging Genetics

“…The selected ROIs, shown in Figure 7, were all mid-line frontal regions, and mostly connected in the MRF prior. The frontal superior orbital, olfactory and rectus regions have all reported schizophrenia deficits, see Nakamura et al (2008), Diaz et al (2011) and Langdon et al (2011), among many others. The left frontal region included the Brodmann area 10, identified by the cross-hair in Figure 7, which is often implicated in schizophrenia (Vogeley et al, 2003; Camchong et al, 2008; Schneiderman et al, 2011).…”