The role of peripheral serotonin in SARS ‐ CoV ‐2 infectivity, COVID ‐19 treatment and long COVID

Gastrointestinal symptoms have emerged as a common, but underappreciated, cause of morbidity in relation to SARS‐CoV‐2 infection and the COVID‐19 pandemic. This manifests as a range of indications including diarrhea, anorexia, nausea, vomiting and abdominal pain. In addition, the gastrointestinal tract may represent a route of viral entry via the epithelial cell layer lining the gut wall. This route of entry could be a significant component of disease pathogenesis, including effects on the nervous system via the gut‐brain axis. In this review, we provide an assessment of the effects of COVID‐19 on the gastrointestinal system, its involvement in disease severity and potential pathways for viral entry and infection in the gastrointestinal tract. We also examine evidence that gut‐derived serotonin is affected by SARS‐CoV‐2 infection, how this may link to symptoms and disease pathogenesis and the potential link to the efficacy of selective serotonin reuptake inhibitors in reducing COVID‐19 severity.