Olfaction in affective and anxiety disorders: a review of the literature.

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.