Of these, six were without residual symptoms after Covid-19 and 17 were control subjects completely free of the disease.
The samples were taken between February and November, 2021 and were analysed for a total of 37 different biomarkers, the researchers said.
They found no detectable SARS-CoV-2 virus in the samples, which had been collected at least three months after the first symptoms of Covid-19 in those who had had the disease.
Further, no significant differences between the participant groups were seen when analysing blood and cerebrospinal fluid for immune activation or brain injury markers, the researchers said in their study published in The Journal of Infectious Diseases.
The findings suggest that post-Covid condition, or long Covid, is not the result of ongoing infection, immune activation, or brain damage, the researchers said.
“The findings enhance our understanding of post-Covid condition,” said Nelly Kanberg, a doctoral student in infectious diseases at the University of Gothenburg.
“The results suggest that the condition is more likely a consequence of events that occur during the acute phase of Covid-19, rather than an ongoing viral infection or persistent inflammation of the central nervous system,” she said.
However, it is still unclear as to what extent is long Covid linked to the body’s inflammatory response during the actual infection, the researchers said, even as many studies globally are currently being carried out on risk factors for long Covid.
Nelly thus emphasised the importance of continued research into the long-term impact of Covid-19 on neuropsychiatric health.
“In order to improve the care and quality of life for those who experience long-term neurological symptoms after Covid-19, we need to understand the underlying causes of post-Covid condition,” said Magnus Gisslen, a professor of infectious diseases at the university.
“This study provides new insights into the condition, and can thus represent a valuable contribution to ongoing discussions and research,” he said.