Olfactory Functioning and Depression: A Systematic Review

Abstract

BackgroundResearch has demonstrated a reduction in olfactory functioning in patients with schizophrenia. This research has led to examination of olfactory functioning in other mental disorders, such as depression. There is a great deal of variation in the results generated from such research, and it remains unclear as to how olfactory functioning is associated with or impacted by depression.MethodThe current review examined the literature in accordance with PRISMA guidelines in order to generate a better understanding of this relationship and to identify if and what aspects of olfactory processing are altered. Through examination of the available literature from the databases PubMed, Ovid Medline, CINAL, and PsychINFO, 15 manuscripts were selected to determine if there was a difference in olfactory processing—specifically central and peripheral processing—between depressed individuals and non-depressed controls.ResultsThe comparison of the 15 studies showed that the majority of studies (9/15, 60%) found a difference in overall olfactory functioning between depressed individuals and non-depressed controls (p < 0.05).LimitationsThere is still a lack of definitive conclusions due to variation of which olfactory process was altered.ConclusionGiven the differences in the methodology and design of these studies, a possible solution that could eliminate the lack of clarity and reduce variation would be to adhere to a single, thorough methodology that examines and separates central and peripheral olfactory processing. Future research employing a uniform and validated methodology could provide more definitive conclusions as to how and if olfactory functioning is related depression.

Associations between Cadmium Exposure and Taste and Smell Dysfunction: Results from the National Health and Nutrition Examination Survey (NHANES), 2011–2014

“…Loss of the ability to taste and smell has a direct impact on safety and quality of life [2]. For example, plenty of recent reports suggest that individuals with taste and smell disorders are more likely to have depressive symptoms [3][4][5][6]. A recent study reported potentially decreased sexual desire among subjects with smell impairment and depressive symptoms [7].…”

Sex differences in main olfactory system pathways involved in psychosexual function

“…5,6 Indeed, the conclusion that females are better than males in many olfactory tasks has been arrived at by most investigators, and a recent meta-analysis confirmed this common belief. [8][9][10][11] It has also been argued that there have been few studies in humans specifically reporting sex differences in olfactory sensitivity per se, suggesting that in addition to the many variables that can affect performance on olfactory tasks, cognitive or emotional appraisal may play an equally important role. [8][9][10][11] It has also been argued that there have been few studies in humans specifically reporting sex differences in olfactory sensitivity per se, suggesting that in addition to the many variables that can affect performance on olfactory tasks, cognitive or emotional appraisal may play an equally important role.…”

“…7 However, reported differences are often small and subject to numerous variables, such as mood, prior experience, age and even socioeconomic status. [8][9][10][11] It has also been argued that there have been few studies in humans specifically reporting sex differences in olfactory sensitivity per se, suggesting that in addition to the many variables that can affect performance on olfactory tasks, cognitive or emotional appraisal may play an equally important role. 12 As a sensor of the chemical environment, the olfactory system is required to respond to a wide range of potential odorants.…”

EUFOREA Rhinology Research Forum 2017: report of the brainstorming sessions on endotype-driven treatment, patient empowerment and digital future in airways care

“…Besides the CRS patients with uncontrolled disease, there was endoscopic sinus surgery (19,20) . Additionally, the stress and cost of anosmia/hyposmia in CRS patients and the potential influence on their mental health (21,22) should be evaluated in this cost estimate, since biologicals seem to have superior results on the improvement of olfaction compared to conventional therapies (14) .…”