New study by US researchers from the Perelman School of Medicine investigates the link between serotonin deficiency and long COVID

A recent study by the Perelman School of Medicine, published in the journal Cell in October 2023, indicates that a deficiency of the hormone serotonin could contribute to the development of long-COVID symptoms and influence their course. Serotonin is a messenger substance that influences the immune system, the nervous system and the inflammatory response, among other things. 

The study found that people with Long COVID had lower serotonin levels compared to recovered persons. The reduced serotonin level could therefore possibly be involved in the development of Long COVID symptoms and lead to impaired brain function and nervous system. Altered blood clotting could also be a consequence of the reduced serotonin level - this can lead to small blood clots ("microthrombi"), which are being discussed as a cause of Long COVID.