Olfactory hallucinations in a population-based sample

Eike Wehling,Josef J Bless,Marco Hirnstein,Bodil Kråkvik,Einar Vedul-Kjelsås,Kenneth Hugdahl,Anne Martha Kalhovde,Frank Larøi

doi:10.1016/j.psychres.2021.114117

Abstract

Olfactory hallucinations referring to olfactory perceptions in the absence of chemical stimuli, occur in non-clinical and clinical populations. Few studies have investigated their prevalence in the general population and little is known about factors triggering and maintaining them such as substance use, severe life events, and mood. We analyzed self-report data from 2500 community dwelling Norwegians, aged 18-96 years, for occurrence of olfactory hallucinations and co-occurring hallucinations in other modalities (auditory, visual, tactile). Analyses included age, sex, self-reported symptoms of depression and anxiety, mental health status, and experience of severe life-events. The results show that 4.2% (95% CI 3.5-5.1%) reported having experienced olfactory hallucinations, and 56% of individuals experiencing olfactory hallucinations also reported these in combination with hallucinations in other modalities. Prevalence varied significantly in terms of age and sex, in that olfactory hallucinations were most frequently reported by young individuals and females. Self-reported symptoms of anxiety and experience of stressful life events were significantly associated with olfactory hallucinations, suggesting that experiencing olfactory hallucinations may negatively affect functioning and may increase the likelihood of developing psychopathology. Findings underline the need to continue to examine olfactory hallucinations albeit with a more comprehensive assessment in order to increase knowledge on this experience.

Highlights

Hallucinations are sensory perceptions occurring in the absence of corresponding sensory stimuli
One-hundred and forty-nine (6%, 95% confidence interval (95% CI) 5.1-6.9) reported that they possibly expe rienced olfactory hallucinations
The odds of reporting olfactory hallucinations in the youngest age group was more than four times higher compared to individuals 60 years of age and older

Summary

Introduction

Hallucinations are sensory perceptions occurring in the absence of corresponding sensory stimuli. In the somatic/olfactory literature, a differentiation is commonly made be tween qualitative and quantitative olfactory functions. E., a person perceives the smell of an orange in the absence of any orange or orange scent). Qualitative ol factory dysfunctions include olfactory hallucinations, termed phantosmia, referring to an odor sensation without a present stimulus Both terms are often used interchangeably, some researchers differentiate between olfactory hallucinations lasting a few seconds and phantosmia lasting longer Quantitative olfactory functions are commonly differentiated into sensitivity referring to the ability to detect an olfactory stimulus and identification referring to a person’s ability to identify an olfactory stimulus (Frasnelli et al, 2004)

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