Long Covid may be caused by lower Serotonin levels

Long COVID is a dumpster fire of brain fog. But, we have new research that suggests the fire is caused by COVID RNA-induced inflammation in the intestines which reduces the neurotransmitter serotonin in the body. That then messes with your memory and energy.

Honestly, this paper is a work of art and I want to take you through it. 

So, this paper has a weak but okay opening where the researchers looked at blood samples of people with Long COVID and saw they had lower circulating serotonin. Cute, but circumstantial. 

But then it gets juicy because next they move into mice to look for why COVID = less serotonin. They found that the immune system reacts to viral RNA by causing inflammation. Not surprising because viruses suck and your body wants them to get out. 

But what is surprising is that virally-caused inflammation in the intestines blocks tryptophan uptake and you need tryptophan to make serotonin. And to add insult to injury, the inflammation also limits the circulation of serotonin in the body. So you’re both making less and transporting less. 

But the thing is that the amount of serotonin circulating in your body doesn’t affect the amount of serotonin in your brain. So, to connect body serotonin levels with the Long COVID brain fog, the researchers did a very hot experiment where they took sad little long Covid mice and artificially activated their sensory neurons which would usually be activated by serotonin in the body. And the mice got better. 

It’s still unclear why our bodies react to COVID by reducing serotonin and also what we can do to help people with Long COVID now that we know this info. Hopefully, we get a follow-up study that I can talk to you about super soon.

Reference: “Serotonin reduction in post-acute sequelae of viral infection.” Wong et al. Cell, 2023.

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