New Study Suggests Reduced Serotonin Levels May Be Linked to Cognitive Difficulties in Long COVID Patients
Researchers at the University of Pennsylvania have conducted a new study that indicates reduced levels of serotonin, a chemical messenger in the brain, may be a possible cause of the cognitive difficulties and memory loss experienced by individuals with long COVID.
The study, which analyzed blood samples from 58 long COVID patients, found that these individuals had significantly depleted levels of serotonin compared to a control group of 30 people who had fully recovered from COVID-19. This suggests a potential pathway linking serotonin depletion in the gut, where most serotonin is produced, to its effects in the brain.
According to the researchers, lingering viral material in the body could trigger the immune system to produce interferons, leading to inflammation and reduced absorption of tryptophan. Tryptophan is an amino acid used to make serotonin. This decreased absorption of tryptophan ultimately results in lower levels of serotonin in the body.
Additionally, the study found that persistent inflammation affected platelets, the blood cells responsible for clotting that carry serotonin throughout the body. This leads to a decrease in circulating serotonin and impairs the activity of the vagus nerve, which plays a crucial role in sending signals between the brain, gut, and other organs.
To further investigate these findings, the researchers conducted experiments on mice that had low serotonin levels and reduced vagus nerve activity due to a viral infection. These mice performed worse on memory tests; however, when serotonin levels were restored, the memory impairments were prevented. This suggests that maintaining appropriate serotonin levels may help mitigate cognitive difficulties associated with long COVID.
While the study highlights a potential link between serotonin levels and long COVID, the researchers acknowledge the need for further human studies to confirm these findings and better understand the underlying mechanisms. Furthermore, the study raises questions about why some long COVID patients in a separate cohort did not exhibit low serotonin levels, indicating that there may be other factors at play.
The researchers hope that their findings will inspire future clinical studies to develop new tools for the diagnosis, monitoring, and treatment of long COVID. Understanding the role of serotonin and its potential impact on cognitive function could pave the way for targeted interventions in long COVID patients and improve their overall quality of life.
Overall, this study provides valuable insight into the potential biochemical factors underlying the cognitive difficulties experienced by individuals with long COVID, highlighting the critical need for further research in this field.