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Researchers from Penn's Perelman School of Medicine found that traces of the COVID virus in longterm patients inhibit the development of serotonin.

Credit: Riley Eastham

A new study led by researchers from Penn's Perelman School of Medicine found that a decrease in serotonin levels is linked to the development of prolonged symptoms in individuals with COVID-19.

According to the study, traces of SARS-CoV-2 in the guts of long COVID-19 patients cause inflammation that prevents the development of serotonin, which is critical to recovery. 

Patients with long COVID-19 experience long-term symptoms like brain fog or fatigue in the months or years following the initial COVID-19 infection. According to the CDC, nearly 7.5% of Americans who are infected with COVID-19 experience long-term symptoms.

“Many aspects of the basic biology underlying long COVID have remained unclear. As a result, we are lacking effective tools for the diagnosis and treatment of the disease,” Maayan Levy, Assistant Professor of Microbiology and senior author of the study, said. 

The new study found that the remaining virus in patients with long COVID-19 triggers patients’ immune system to release interferons, proteins that continue to fight the virus. This, in turn, affects patients’ absorption of the amino acid tryptophan, which is critical to the development of serotonin.

Serotonin, commonly referred to as the “happy hormone,” is responsible for memory, happiness, body temperature regulation, sleep, sexual behavior, and hunger. A lack of serotonin is correlated with depression, anxiety, mania, and other health conditions. 

Because of the study results, researchers are looking into new ways of treating long COVID-19 by examining serotonin. This novel approach marks a breakthrough in developing treatments for long-term symptoms.  

“Our findings may not only help to untangle some of the mechanisms that contribute to long COVID, but also provide us with biomarkers that can help clinicians diagnose patients and objectively measure their response to individual treatments,” Levy said.

Levy previously received the National Institute of Health Director’s Award, which is granted to scientists undertaking innovative research with a broader impact on pressing biomedical challenges.

“There has been some evidence to suggest that SSRIs could be effective in preventing long COVID, and our research now presents an opportunity for future studies to select specific patients for a trial who exhibit depleted serotonin, and to be able to measure response to treatment,” Benjamin Abramoff, Assistant Professor of Clinical Physical Medicine and Rehabilitation and senior author of the study, said.