Though we may not realize it, we rely heavily on our sense of smell to get through the day. Our ability to smell alerts us to dangers in our environment, keeps us aware of our personal hygiene, and is responsible for most of our perception of taste. For those with some form of olfactory dysfunction, this information is noticeably absent.  Forms of olfactory dysfunction include hyposmia (the partial loss of the sense of smell) and anosmia (the total loss of the sense of smell). They can be caused by issues ranging from sinus infections to head trauma, but they are most commonly caused by post-viral upper respiratory infection (Smeets et al., 2009). Throughout the COVID-19 pandemic, loss of the sense of smell has emerged as a recognizable symptom of the virus. For most patients, this is temporary and they regain their sense of smell within two to three weeks. For a growing number of the population, however, this loss persists even after they have otherwise recovered (CDC, 2021). The disorienting experience of olfactory dysfunction has been proven to have a significant effect on mental health, with many of those affected experiencing anxiety and depression (Smeets, et al., 2009).

During the course of a typical upper respiratory virus, nasal mucosal edema may occur, resulting in nasal inflammation. This can be noticed in symptoms such as a stuffy nose. After the patient has recovered, the swelling of the olfactory mucosa can persist, which causes damage to the olfactory neuroepithelium – the tissue containing sensory nerve endings in the nose (Jiang, 2020). However, there is a growing amount of evidence that suggests that olfactory dysfunction caused by COVID-19 results from the loss of function of supporting cells in this tissue, which then changes olfactory sensory neurons (Jiang, 2020).

Although it is easier to diagnose olfactory conditions now more than ever before thanks to diagnostics such as the Sniffin’ Sticks Test, many patients seeking treatment have found difficulty in getting diagnosed (Haxel et al., 2012). It can be difficult to narrow down what caused the olfactory dysfunction, and up until recently, the discussion of conditions such as anosmia [and hyposmia] was not as prevalent. Since olfactory dysfunction stemming from COVID-19 is new, patients may experience even more uncertainty about their condition and if there is hope for recovery (Newhouse, 2020). 

In a 2009 study conducted by Monique A. M. Smeets and Maria G. Veldhuizen, members of an anosmia support group were compared with a control group to assess if loss of smell had an impact on their health-related quality of life. Participants filled out a survey made up of four questionnaires in which they were asked about their level of olfactory dysfunction as well as their mental health, which was assessed via the 36-Item Short-Form RAND Health Survey (SF-36) and the Beck Depression Inventory (BDI). The study found that anosmics have a significantly lower quality of life when compared to the control group. In particular, the anosmia group scored higher on the BDI, and their responses to the SF-36 questionnaire revealed that their quality of life was impacted by “feelings of depression and nervousness.” (Smeets et al., 2009).

In another study exploring the association between olfactory dysfunction and depression, Kohli et al. (2016) compiled data from previous studies to find a correlation between the two conditions. Studies on depression were examined for data about olfactory dysfunction, and vice versa. They found significant proof of “a reciprocal relationship between olfaction and depression.”  BDI scores increased with the severity of olfactory impairment, as anosmics scored higher on the BDI than those without any form of olfactory dysfunction. Most notably, data from one of the examined studies revealed that 19 out of the 25 patients (or 76%) with olfactory dysfunction stemming from an upper-respiratory infection were depressed (Kohli et al., 2016).

The connection between olfactory dysfunction and depression is not surprising. Those without their sense of smell become aware of the loss in many aspects of their life. Socialization becomes more difficult, especially when it centers around food. Patients with olfactory dysfunction may also struggle with maintaining awareness of their personal hygiene, which could lead to further isolation. Additionally, not being able to detect dangers in the environment causes patients to become worried over their ability to keep themselves and their family safe. They may accidentally prepare or ingest spoiled food, have difficulty noticing the presence of allergens, and not notice gas or smoke. The overall experience of olfactory dysfunction has been proven to be emotionally taxing and far-reaching (Croy et al., 2014). 

However, those with a form of olfactory dysfunction can take steps to feel more secure and connected. Accepting the situation and making the best out of it sounds easier said than done, but a large number of patients frequently employ emotion-based and problem-based strategies to help adapt to their circumstances. For example, purchasing devices such as smoke detectors and enlisting the help of family and friends while preparing food can help create a sense of security (Croy et al., 2014). Additionally, treatment using steroids and smell-training exercises may help patients to regain their sense of smell (Marshall, 2021).  Most importantly, perhaps, is the knowledge that patients are no longer as isolated in this experience as was the case in the past. A quick Facebook search shows many support groups for olfactory dysfunction, such as “Covid Anosmia/Parosmia Support” which has over 25,000 members. As we continue to learn more about the COVID-19 recovery process, breakthroughs in the treatment of olfactory dysfunction are just on the horizon.

References

Smeets, M., Veldhuizen, M. G., Galle, S., Gouweloos, J., de Haan, A., Vernooij, J., Visscher, F., & Kroeze, J. (2009). Sense of smell disorder and health-related quality of life. Rehabilitation psychology, 54(4), 404–412. https://doi.org/10.1037/a0017502

Kohli, P., Soler, Z. M., Nguyen, S. A., Muus, J. S., & Schlosser, R. J. (2016). The Association Between Olfaction and Depression: A Systematic Review. Chemical senses, 41(6), 479–486. https://doi.org/10.1093/chemse/bjw061

Croy, I., Nordin, S., & Hummel, T. (2014). Olfactory disorders and quality of life–an updated review. Chemical senses, 39(3), 185–194. https://doi.org/10.1093/chemse/bjt072

Jiang, K. (2020, July 24). How COVID-19 Causes Loss of Smell. How COVID-19 Causes Loss of Smell | Harvard Medical School. https://hms.harvard.edu/news/how-covid-19-causes-loss-smell 

Seiden A. M. (2004). Postviral olfactory loss. Otolaryngologic clinics of North America, 37(6), 1159–1166. https://doi.org/10.1016/j.otc.2004.06.007

Marshall, M. (2021, January 14). COVID’s toll on smell and taste: what scientists do and don’t know. Nature News. https://www.nature.com/articles/d41586-021-00055-6. 

Haxel, B. R., Nisius, A., Fruth, K., Mann, W. J., & Muttray, A. (2012). Defizite der ärztlichen Beratung bei Riechstörungen. HNO, 60(5), 432–438. https://doi.org/10.1007/s00106-011-2448-z 

Centers for Disease Control and Prevention. (2021). Post-COVID Conditions. Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/long-term-effects.html. 

Leo Newhouse, L. I. C. S. W. (2020, October 19). Coping with the loss of smell and taste. Harvard Health. https://www.health.harvard.edu/blog/coping-with-the-loss-of-sense-of-smell-and-taste-2020101921141.