Olfaction in Affective and Anxiety Disorders: A Review of the Literature

Abstract

Background: Olfaction and its relation to mental health is an area of growing interest. Brain areas linked to olfaction partially overlap with brain areas involved in psychiatric disorders; consequently, the study of olfactory function allows us to explore the integrity of these brain areas with a non-invasive and effective method. Accordingly, the aim of this paper is to review olfactory function in affective and anxiety disorders. Methods: For this purpose, an extensive literature review of English-language studies on olfactory function in patients with the aforementioned pathologies was performed using several online databases. A manual search of relevant journals and books as well as reference lists from selected papers was also performed. Results: The available data show that depressed patients are usually characterised by preserved olfactory function, except for detection threshold, where contrasting reports have been found. Bipolar disorder has been studied to a lesser extent, but the findings have shown a lack of impairment in most cases. Research on seasonal affective disorders is scant, and future studies are needed to make conclusions. Anxiety disorders have been scarcely approached, but the results note identification deficits in obsessive-compulsive and posttraumatic stress disorders. Conclusions: Olfactory assessment appears to be a complementary, valuable research tool in the study of psychiatric disorders. However, further investigation is needed to improve our understanding of olfactory function in these disorders.

Cortico-subcortical metabolic correlates of olfactory processing in healthy resting subjects

“…Interestingly a significant negative correlation (r = −0.65; Figure 4B) between a quantitative aspect of a pure odorant (IVAS OC) with a qualitative one (OI) was found in the present study by using validated tests36. In particular this trend of correlation could depict a daily life aspect in which an increase in subjective intensity of a pure odorant target is commonly associated to reduction in general odor identification.…”

Heightened Olfactory Sensitivity in Young Females with Recent-Onset Anorexia Nervosa and Recovered Individuals

“…Moreover, the factor structure of the BYI indicate that the two scales tap into the same domain of emotional distress. [48] However, depressive disorders reduce the ability of olfaction,[21] whereas the presence of anxiety enhances olfaction,[22] which is why we analyzed both scales. Participants also completed the Eating Disorder Inventory, third edition (EDI-3),[49] to describe thoughts and emotions related to AN.…”

“…To assess potential impact of factors known to be associated with olfaction we repeated the ANOVAs of the two olfaction test scores four times, each time excluding the participants with the characteristic in question: smoking on a daily basis (N = 15; 3 first-episode AN, 5 recovered, 7 controls),[53] current major depressive disorder (N = 11; 8 first-episode AN, 3 recovered), 37 anxiety disorder other than OCD (N = 9; 4 first-episode AN, 5 recovered),[22] serotonergic medication (N = 3 recovered). [15] If these sensitivity analyses did not change the main results, then the subgroups were kept in the main analysis to maintain statistical power.…”

“…[21,22] Thus, depression and anxiety may influence findings in individuals affected by AN due to their common co-occurrence. [23] Indeed, a study of adolescents with AN observed increased identification ability only when participants with psychiatric comorbidity, mainly depression, were omitted from analysis.…”

Olfactory and executive dysfunctions following orbito-basal lesions in traumatic brain injury

“…The increasingly accepted relationship between post-traumatic anosmia and frontal lobe involvement is further supported by the difficulties that patients with anosmia exhibit in executive functions [19] and affective states [20]. In fact, these functions rely on the same regions as olfactory processing-frontal regions for executive functions and limbic regions for emotions [21].…”