In their meta-analysis, published in The Lancet Psychiatry, Jonathan Rogers and colleagues1 highlighted common neuropsychiatric symptoms in patients with severe acute respiratory syndrome (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) compared with COVID-19 and emphasised the need to recognise these potential problems in the management of COVID-19. Sommer and Bakker2 called for caution when making direct comparisons between these coronaviruses because chronic sequelae of COVID-19 are still unknown and confounding factors cannot be excluded.
We would like to draw attention to an important factor that was not alluded to in the meta-analysis.1 Olfactory dysfunction (anosmia and hyposmia) has a strikingly high prevalence (60–70%) in patients with severe acute respiratory syndrome 2 (SARS-CoV-2) compared with other coronaviruses.3 Olfactory dysfunction was not reported as a symptom during past SARS-CoV and MERS-CoV outbreaks. In our community care facilities, we have seen patients with SARS-CoV-2 and pure olfactory dysfunction without nose block or other signs of respiratory infections. These individuals were anxious about permanently losing their sense of smell, and in some cases their sense of taste. The anxiety is understandable because olfactory dysfunction usually occurs early during infection with SARS-CoV-2 and can be severe, with some patients experiencing severe dyspnoea.3
In animal models, disruption of olfactory pathways and experimental removal of the olfactory bulb can lead to neurochemical and behavioural changes seen in depressive states that are reversible with anti-depressant drugs.4 In humans, olfactory dysfunction has been reported in patients with depression and cognitive impairment.4, 5 In a study of 6783 adults, better olfactory performance was associated with better cognitive performance.5
The potential neuropsychiatric burden associated with cranial nerve problems, such as olfactory and gustatory dysfunctions, is still largely unexplored in the COVID-19 pandemic. Olfactory dysfunction can lead to both short-term and long-term neurological and neuropsychiatric complications that need to be investigated. Recognising neuropsychiatric sequelae of olfactory dysfunction and other neurological complications, such as stroke as a result of COVID-19, and facilitating closer longitudinal follow up of patients with structural or functional brain damage will improve their quality of care and mental wellbeing.
Acknowledgments
We declare no competing interest.
References
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