Buckle up for a surprisingly exciting crash course on serotonin.
The results of a new study on long Covid are out, and they’re more than promising — they might even be groundbreaking.
Conducted by researchers at the University of Pennsylvania, the study suggests there may be a strong connection between serotonin levels, gut health, and the development of long Covid. Even more exciting, scientists now believe it might eventually be possible to treat certain symptoms of long Covid, like brain fog and memory loss, with selective serotonin reuptake inhibitors (SSRIs), like Prozac.
Here’s how the researchers of the study came to this conclusion, along with an (extremely efficient, we promise!) explanation of what the heck serotonin has to do with gut health.
What did the study reveal about long Covid patients?
In this study, researchers analyzed blood samples of 58 patients who had been experiencing long Covid symptoms for anywhere from three to 22 months since they were initially infected with the virus. Then they compared those blood samples to two control sets: One set was comprised of 30 patients who had no Covid symptoms after contracting the virus, and the other included 60 patients who were in the early stages of a Covid infection.
Researchers noted in their findings, published in the scientific journal Cell, that serotonin levels generally decreased after a Covid infection took place. As one of the scientists told the The New York Times, this wasn’t exactly surprising on its own, since this serotonin drop is a common occurrence for many viral infections. Usually, those levels return to normal when a viral infection is over.
But when researchers analyzed the blood samples of those suffering from long Covid symptoms, they noticed that serotonin levels did not recover to their pre-infection levels. So what, exactly, does that tell us?
What does serotonin have to do with long Covid?
It’s important to clarify that serotonin isn’t just a “happiness” hormone, as some may think. It’s also an essential part of our body’s regulatory process — it helps to keep our bowels moving, ensures we get a good night’s sleep, and allows our nervous system to operate appropriately.
Here’s where it gets really interesting: Serotonin is also connected to our brain and memory function — and seeing as how brain fog is a common symptom of long Covid, this is why researchers have been trying to determine for a while now whether there’s any connection between serotonin and these extended side effects.
In the University of Pennsylvania study, researchers found remnants of the Covid virus in the gut of those suffering from long Covid symptoms. This was immediately compelling to them, since the gut is also the source for 95 percent of the body’s serotonin production.
Here’s the hypothesis the researchers came to as a result, to put it as simply as possible: If remnants of the Covid virus linger in the gut, then those remnants might be inspiring the gut to send out inflammation signals to the body. Those inflammation signals tend to inhibit the body’s ability to absorb the amino acid tryptophan, and that absorption process is essential to the gut’s production of serotonin. When we can’t produce the ideal levels of serotonin, that disrupts the ongoing communication between the body and the brain, which could potentially explain the brain fog, memory loss, and other forms of mental impairment that tend to come with long Covid.
How SSRIs like Prozac might serve as a future treatment for long Covid
If this connection between the gut, serotonin production, and brain fog actually is what’s happening with long Covid, then how do we fix it?
The researchers of the study have a hypothesis for that, too.
In an accompanying animal study, University of Pennsylvania researchers found the same depleted serotonin levels and cognitive dysfunction within mice who also had remnants of the virus in their guts. The researchers gave the mice doses of SSRIs, which worked to restore serotonin levels and cognitive function to pre-infection levels.
The implications of these two studies are obviously major: If long Covid symptoms do originate in the gut, and it is possible to treat those symptoms with SSRIs, that would be a massive breakthrough in understanding how the pandemic has affected us.
But we shouldn’t jump for joy just yet. The University of Pennsylvania study was notably quite small, and there have been similar studies that didn’t provide the same conclusions regarding serotonin levels.
But this research could definitely be an exciting step forward. The next step would be a bigger study with a much larger sample size, and if that study reinforces researchers’ hypothesis about SSRIs being used to treat long Covid symptoms, a clinical trial could follow shortly after.
There’s a long road of research, trials, and hypothesis-making ahead — but scientists from all over the world are celebrating this study as an exciting development. Adupa Rao, M.D., an associate professor of clinical medicine at the Keck School of Medicine at the University of Southern California, spoke to Healthline about what this study means for future Covid research: “This research highlights how complex this long Covid diagnosis can be,” he said. “It requires really thinking outside the box to establish a diagnosis and hopefully a treatment option in the near future.”
