Depressed mood or anxiety exhibited in Covid-19 patients may possibly be a sign the virus affects the central nervous system, according to a new study.
The findings, published in the journal The Laryngoscope, revealed that these two psychological symptoms 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.
"The unexpected results 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," said study researcher Ahmad Sedaghat from the University of Cincinnati in the US.
For the study, the research team 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 at Kantonsspital Aarau in Aarau, Switzerland.
The severity of the loss of smell or taste, nasal obstruction, excessive mucus production, fever, cough and shortness of breath during COVID-19 were assessed.
At the time of enrollment in the study, when participants were experiencing Covid-19, 47.4 per cent of participants reported at least several days of depressed mood per week while 21.1 per cent reported depressed mood nearly every day.
In terms of severity, 44.7 per cent of participants reported expressing mild anxiety while 10.5 per cent reported severe anxiety.
"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,"
Sedaghat said researchers have long thought that the olfactory tract may be the primary way that coronaviruses enter the central nervous system.
Studies using mouse models of that virus have shown that the olfactory tract, or the pathway for communication of odours from the nose to the brain, was a gateway into the central nervous system and infection of the brain.
"These symptoms of psychological distress, such as depressed mood and anxiety are central nervous system symptoms if they are associated only with how diminished is your sense of smell," Sedaghat said.
"This may indicate that the virus is infecting olfactory neurons, decreasing the sense of smell, and then using the olfactory tract to enter the central nervous symptom," he noted.