Can Sensitivity to Common Smells Sniff Out Depression, Anxiety?

Sensitivity to specific common odors correlates with symptoms of depression or anxiety, new research shows.

A study of more than 400 participants showed that symptoms of anxiety were associated with heightened awareness of floral scents or kitchen smells, while depression was to increased awareness of linked social odors including “good” and “bad” smells of other people.

“The assessment of meta-cognitive abilities may be a useful tool in assessing depressive, anxiety, and social anxiety symptoms,” study investigator Cinzia Cecchetto, PhD student, postdoctoral researcher, Department of General Psychology, University of Padua, Italy, told Medscape Medical News.

The findings were published online April 13 in the Journal of Affective Disorders.

Smell Perception

Previous studies have shown a strong relationship between reduced odor detection and symptoms of depression, with less clear evidence of a link between olfactory perception and symptoms of anxiety, Cecchetto said.

However, few studies have investigated what extent individuals with symptoms of anxiety or depression are aware of, or pay attention to, odors in their environment, she added.

The study included 429 healthy participants (76.9% women, aged 18 to 45 years) recruited through social media. The age cut-off was 45 because evidence shows that olfactory perceptions start to decline at that time of life, Cecchetto noted.

Participants completed psychological questionnaires, including the Beck Depression Inventory-II, the Beck Anxiety Inventory, and the Liebowitz Social Anxiety Scale.

They also completed olfactory questionnaires, including the Odor Awareness Scale for evaluating the degree to which an individual focuses on olfactory stimuli such as that from food; the Affective Impact of Odor scale for assessing how odors affect liking and memory for people, places, and things; the Vividness of Olfactory Imagery Questionnaire, which examines the ability to form olfactory images such as fragrances from a garden; and the Social Odor Scale, which assesses awareness of social odors such as sweat in everyday interactions.

Results showed that general anxiety symptoms were a significant predictor of higher levels of awareness of common odors.

The investigators note that this finding is similar to that from previous research in which patients with panic disorder reported higher olfactory sensitivity, reactivity, and awareness of odors compared with a control group. It is also in line with clinical features of anxiety, in which individuals maintain heightened vigilance, hyperarousal, and action readiness to respond to sudden danger.

Individuals with social anxiety symptoms reported being less attentive toward social odors.

This finding is at odds with the tendency of individuals with social anxiety to continuously monitor the environment for signs of potential negative evaluations by others.

In addition, it contradicts findings from previous studies showing that social anxiety is associated with enhanced startle reactivity and faster processing of social odor anxiety signals compared with healthy controls, the controversies note.

Clinical Implications?

“A possible explanation for these conflicting findings could be that in our study we did not present real odors to participants, but asked them if they usually pay attention to these odors,” lead author Elisa Dal Bò, PhD student, Padova Neuroscience Center and Department of General Psychology, University of Padua, told Medscape Medical News .

“Indeed, other studies have shown individuals with social anxiety focus their attention more on themselves and avoid paying attention to other people during social interactions,” she added.

Depressive symptoms were a significant predictor of higher social odor awareness and lower affective responses to odors. Some past studies showed that “depression is characterized by an increased attention to social stimuli induced by the fear of social rejection,” Dal Bò noted.

The current findings showing that depression symptoms were associated with higher social odor awareness while social anxiety symptoms were associated with lower social odor awareness are at odds with what was hypothesized, Cecchetto said.

“Actually we were expecting the opposite pattern, and that’s why it’s important to investigate more deeply these meta-cognitive abilities,” she said.

Neither depressive nor anxiety symptoms were significant predictors of olfactory imagery.

Female respondents were more attentive to, and aware of, odors than men. This finding is “quite common in the literature,” Cecchetto noted.

Although preliminary, the results could eventually have clinical implications, the investigators note. Olfactory metacognitive abilities, obtained through questionnaires, could be used to assess potential olfactory impairments, which could signal future risk for psychiatric symptoms.

However, the relatively young age of participants in the study and the prevalence of women limits the generalization of the findings, the researchers note. In addition, clinical symptoms were self-reported and were not verified by healthcare professionals.

“Not Enough Evidence”

Commenting for Medscape Medical NewsPhilip R. Muskin, MD, professor of clinical psychiatry, Columbia University Medical Center, New York City, said he did not find the surprising results.

For example, that individuals with social anxiety are not particularly aware of others’ smell “makes perfect sense” because “people with social anxiety disorder are concerned with themselves,” he said.

Muskin, who has an interest in and has written about olfactory function, was not involved with the research.

He noted several study limitations. First, participants just reported on their smell awareness, but “having people actually smell stuff might have been more interesting.”

In addition, the study population was relatively young, mostly women, and women’s olfactory sensitivity changes throughout the menstrual cycle, Muskin said.

“We don’t know where these women are in their cycles when they’re reporting their awareness of odors,” he said. “It would be good to know if the women were all in the luteal phase or were premenstrual because that might correlate with their anxiety or depressive symptoms.”

Asking a patient about smell awareness may provide some insight when assessing for symptoms of depression, along with obtaining details on such things as sleep, Muskin noted.

However, he does not think the new findings are enough to include olfactory awareness in the interview process. “It’s not enough evidence to use as a clinical tool for diagnosis and I don’t see this is clinically useful yet.”

J Affect Disord. Published online April 13, 2022. Abstract

The study was supported by the European Commission Horizon 2020 research and innovation program and the Austrian Science Fund. The investigators and Muskin have reported no relevant financial relationships.

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