A team of scientists is proposing a new explanation for some cases of long Covid, based on their findings that serotonin levels were lower in people with the complex condition.
In their study, published on Monday in the journal Cell, researchers at the University of Pennsylvania suggest that serotonin reduction is triggered by remnants of the virus lingering in the gut. Depleted serotonin could especially explain memory problems and some neurological and cognitive symptoms of long Covid, they say.
Why It Matters: New ways to diagnose and treat long Covid.
This is one of several new studies documenting distinct biological changes in the bodies of people with long Covid — offering important discoveries for a condition that takes many forms and often does not register on standard diagnostic tools like X-rays.
The research could point the way toward possible treatments, including medications that boost serotonin. And the authors said the biological pathway that their research outlines could unite many of the major theories of what causes long Covid: lingering remnants of the virus, inflammation, increased blood clotting and dysfunction of the autonomic nervous system.
“All these different hypotheses might be connected through the serotonin pathway,” said Christoph Thaiss, a lead author of the study and an assistant professor of microbiology at the Perelman School of Medicine at the University of Pennsylvania.
“Second of all, even if not everybody experiences difficulties in the serotonin pathway, at least a subset might respond to therapies that activate this pathway,” he said.
“This is an excellent study that identifies lower levels of circulating serotonin as a mechanism for long Covid,” said Akiko Iwasaki, an immunologist at Yale University. Her team and colleagues at the Icahn School of Medicine at Mount Sinai recently published a study that identified other biological changes linked to some cases of long Covid, including levels of the hormone cortisol. These studies could point to specific subtypes of long Covid or different biological indicators at different points in the condition.