Depressed mood or anxiety exhibited in COVID-19 patients may possibly be a sign the virus affects the nervous system, according to a study which says these psychological symptoms may be linked to the widely reported disruption of the sense of smell and taste caused by the viral infection.

The research, published in The Laryngoscope, noted that the two symptoms related to mental health were most closely associated with a loss of smell and taste rather than the more severe indicators of the novel coronavirus such as shortness of breath, cough or fever.

“If you had asked me why would I be depressed or anxious when I am COVID positive, I would say it is because my symptoms are severe and I have shortness of breath or I can’t breathe or I have symptoms such as cough or high fever,” said study co-author Ahmad Sedaghat from the University of Cincinnati in the US.

“None of these symptoms that portended morbidity or mortality was associated with how depressed or anxious these patients were,” explained Sedaghat.

He said the only element of COVID-19 that was associated with depressed mood and anxiety was the severity of patients’ loss of smell and taste.

However, the study cautioned that the there may not be a causal link between the disruption of the sense of smell in COVID-19 and the psychological symptoms.

“Our study should be interpreted within the context of its limitations, the most conspicuous of which is that we cannot show any direct causal link between chemosensory dysfunction in COVID-19 and emotional disturbance,” the researchers wrote.

In the study, they conducted a prospective, cross-sectional telephone questionnaire study which examined characteristics and symptoms of 114 patients who were diagnosed with COVID-19 over a six-week period.

From the data collected, the scientists assessed the severity of the loss of smell or taste, nasal obstruction, excessive mucus production, fever, cough and shortness of breath during COVID-19.

At the time of enrolment in the study, when participants were experiencing COVID-19, the researchers said 47.4 per cent of participants reported at least several days of depressed mood per week.

They said nearly a fifth of the participants reported depressed mood nearly every day.

In terms of severity, the study noted that 44.7 per cent of the participants reported expressing mild anxiety while 10.5 per cent reported severe anxiety.

“The unexpected finding that the potentially least worrisome symptoms of COVID-19 may be causing the greatest degree of psychological distress could potentially tell us something about the disease,” Sedaghat said.

“We think our findings suggest the possibility that psychological distress in the form of depressed mood or anxiety may reflect the penetration of SARS-CoV-2, the virus that causes COVID-19, into the central nervous system,” the researchers noted.

Sedaghat believes there may be more central nervous system penetration of the virus than previously reported.

“This really opens up doors for future investigations to look at how the virus may interact with the central nervous system,” he said.