A recent study published in the journal Cell suggests that lower levels of serotonin in the gut may be linked to long Covid in some patients. The researchers at the University of Pennsylvania propose that remnants of the coronavirus lingering in the gut may stifle the production of serotonin, an important neurotransmitter. This reduction in serotonin could explain memory problems and some neurological and cognitive symptoms associated with long Covid.
The study adds to a growing body of research that highlights distinct biological changes in individuals with long Covid. These findings are crucial as the condition often does not register on standard diagnostic tools like X-rays, making it challenging to diagnose and treat effectively.
The research also offers potential avenues for treatment, including medications that boost serotonin. The authors suggest that the biological pathway outlined in their study could connect various theories of what causes long Covid, such as lingering viral remnants, inflammation, increased blood clotting, and dysfunction of the autonomic nervous system.
The study analyzed blood samples from 58 long Covid patients and compared them to samples from individuals without post-Covid symptoms and those in the early stages of infection. The researchers found that serotonin levels did not recover to pre-infection levels in individuals with long Covid, unlike other metabolites that returned to normal. Stool samples from some long Covid patients also contained viral particles, further supporting the link between the virus in the gut and serotonin reduction.
The team proposes a pathway where viral remnants trigger the immune system to produce interferons, which cause inflammation and reduce the body's ability to absorb tryptophan, an amino acid necessary for serotonin production. Blood clots that can form after a coronavirus infection may also hinder serotonin circulation. Depleted serotonin then disrupts the vagus nerve system, potentially leading to memory problems and cognitive issues.
It's important to note that the study's findings need confirmation through further research, as the sample size was relatively small. Additionally, not all long Covid patients in other studies showed depleted serotonin, indicating that serotonin reduction may only occur in individuals with multiple serious symptoms.
Moving forward, researchers aim to identify biomarkers for long Covid that can aid in diagnosis. The study suggests three potential biomarkers: the presence of viral remnants in stool, low serotonin levels, and high levels of interferons. Clinical trials are also underway to test various treatments for long Covid, including a trial led by the researchers at the University of Pennsylvania to test Prozac and possibly tryptophan.
Overall, this study provides valuable insights into the potential link between serotonin reduction and long Covid, offering hope for improved diagnosis and treatment options in the future.