So-called Long COVID occurs when symptoms of the virus persist for more than 12 weeks after the initial infections. Those symptoms typically included extreme fatigue, breathlessness, muscle weakness, and cognitive dysfunction or "brain fog."
To date, no effective treatments have been discovered.
It's estimated to affect at least 10 percent of people infected with COVID, with far higher incidence among those hospitalized.
The study by a group of scientists at the University of Pennsylvania, published Monday, Oct. 16 in the journal Cell, found that serotonin levels were lower in people with Long COVID and caused by remnants of the virus lingering in the gut.
Serotonin depletion causes cognitive impairment through reduced sensory neuron activity, the study noted.
"These findings provide a possible explanation for neurocognitive symptoms associated with viral persistence in Long COVID, which may extend to other post-viral syndromes," the study states.
The findings point to a possible treatment for Long COVID: medications that increase serotonin levels.
"Our animal models demonstrate that serotonin levels can be restored and memory impairment reversed by precursor supplementation or SSRI treatment," the study said.
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