- Our sense of smell is tied up with our memories and emotions. What happens to this link after experiencing anosmia because of COVID?
- Olfactory training seems to be able to help people regain their sense of smell.
- Treating our sense of smell like a muscle that can be developed means we can strengthen it if it becomes weakened.
- How a renewed sense of smell might unlock lost memories and a more vibrant emotional life remains a question.
Research now suggests that for many COVID survivors with long-term sensory loss, these symptoms may also be linked to depressed mood. Interestingly, and disturbing for those experiencing it, some are struggling with parosmia, a disorder that causes previously normal odours to develop a new, often unpleasant aroma.
Smell, Emotion, and Memory
We know that smells, and indeed our sense of taste, are handled by the olfactory bulb — a structure in the front of the brain that relays information to other areas for further processing. These include the amygdala, hippocampus, and wider limbic system — brain regions related to emotion and memory.
Anosmia can have a profound effect on our experience of the world. Our sense of smell is closely linked with memory, probably more so than any of our other senses. Those with full olfactory function may think of smells that evoke particular memories; for me, the scent of a particular type of green tea conjures up recollections of an especially enjoyable trip to Japan. Our sense of smell is also highly emotive, partly connecting us through universal experiences in which we have similar emotional reactions of disgust to certain odours, as well as unique, complex emotional experiences in which we can have different perceptions of the same smell. One person may find a particular brand of perfume to be ‘powerful’ and ‘heady’, with someone else describing it as ‘overpowering’ and ‘nauseating’.
A 2016 review of the existing research on anosmia and depression showed that the relationship between mood and smell loss appears to operate in both directions: People with depression are more likely to have problems with a sense of smell than healthy controls, and people with anosmia are more likely to have symptoms of depression — and the greater the loss of smell, the more severe the depressive symptoms.
A web-based survey completed by 322 adults with COVID that brought on a sudden change in smell or taste showed 56% reporting decreased enjoyment in life, and 43% reporting feeling depressed, after losing their sense of smell. Most people seem to recover their sense of smell within a month or two after their experience of COVID, based on this study. However, for a minority of patients with residual smell or taste loss, olfactory training might be helpful.
Olfactory training involves repeated and related sniffing of a set of strong smells (e.g. lemon, cloves, eucalyptus, orange) for 20 seconds each, at least twice a day, for a period of at least three months. (The protocols vary a little, but the essence remains the same.) The treatment seems effective in wider populations of people affected by olfactory dysfunction, and it has been used with COVID survivors. The parosmia that I mentioned earlier seems to be a stage in the recovery of smell for some patients; olfactory training may help to shape this recovery onto a better track.
As people age, they lose their sense of smell. But if you consider your nose like a muscle that can be strengthened, then giving it a workout through different odours and ways to sniff them can help bring back lost dimmed abilities, and even add new vitality and sensitivity to our sense of smell that is different to what previously existed.
How COVID-Induced Anosmia Is Linked to Emotional Experience and Memory
Once a sense of smell can be recovered, the key to those doors of anosmia-locked memories may be flung open once again — a life re-filled with rich memories and emotions triggered through being able to smell.
But does our sense of smell change because of COVID and indeed, olfactory training? Do the new “keys” that we develop fit the locks of our memories and emotions well enough for them to be available to us once again? The hopeful answer is yes if the wider population’s experience of olfactory training is anything to go by. But COVID-induced anosmia may be an interesting and fertile ground to understand more about how our sense of smell is so important to our experience of our world, what happens when we lose it, and what might change when we get it back again.
Moein ST, Hashemian SMR, Mansourafshar B, Khorram-Tousi A, Tabarsi P, Doty RL. Smell dysfunction: a biomarker for COVID-19. Int Forum Allergy Rhinol. Published online April 17, 2020.
Kohli P, Soler ZM, Nguyen SA, Muus JS, Schlosser RJ. The Association Between Olfaction and Depression: A Systematic Review. Chem Senses. 2016;41(6):479-486. doi:10.1093/chemse/bjw061
Reiter ER, Coelho DH, Kons ZA, Costanzo RM. Subjective smell and taste changes during the COVID-19 pandemic: Short term recovery. Am J Otolaryngol. 2020;41(6):102639. doi:10.1016/j.amjoto.2020.102639
Whitcroft KL, Hummel T. Clinical diagnosis and current management strategies for olfactory dysfunction: a review. JAMA Otolaryngol Head Neck Surg. 2019;1:1-9.
Mackenzie E Hannum, Vicente A Ramirez, Sarah J Lipson, Riley D Herriman, Aurora K Toskala, Cailu Lin, Paule V Joseph, Danielle R Reed, Objective Sensory Testing Methods Reveal a Higher Prevalence of Olfactory Loss in COVID-19–Positive Patients Compared to Subjective Methods: A Systematic Review and Meta-Analysis, Chemical Senses, Volume 45, Issue 9, November 2020, Pages 865–874, https://doi.org/10.1093/chemse/bjaa064