Surprising Serotonin Link to Long COVID

doctor looking at research

Brain fog. It’s one of the most common—and frustrating—symptoms associated with long COVID. That’s the lingering condition affecting nearly 1 in 5 people who get infected with SARS-CoV-2, the virus that causes COVID-19. For several years now, experts have been trying to discover the elusive causes of brain fog and other neurocognitive and mental health symptoms associated with long COVID.

Exciting new research may provide some answers. A 2023 study published in the journal Cell has found a link between brain fog in long COVID and low serotonin levels. Let’s explore what this means for the millions of people struggling with long COVID.

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Emerging research has found a link between low serotonin levels and long COVID.


Also called post COVID-19 syndrome, long COVID is defined as symptoms lasting months or years after being infected with the virus. Long COVID has been associated with over 200 symptoms, including neurocognitive issues and mental health problems, such as:

  • Brain fog
  • Memory loss
  • Anxiety
  • Depression
  • Irritability
  • Mood lability
  • Anger
  • Poor attention
  • Difficulty thinking
  • Trouble problem-solving
  • Confusion
  • Insomnia

These effects have earned the notorious syndrome the names “COVID brain” and “neuro COVID.”

Brain fog has emerged as one of the top long COVID symptoms. Statistics about its prevalence range from 45% to 70% of all COVID long-haulers, according to findings in JAMA Open Network and Frontiers in Aging Neuroscience.

People who have been infected with the virus that causes COVID-19 are also at dramatically increased risk of developing mental health conditions. These COVID-related mental disorders have also been tied to the rising use of alcohol, prescription medications, and recreational drugs.

Brain-imaging studies including those at Amen Clinics using SPECT scans show that long COVID harms the brain in many ways. Among the damaging effects seen in long COVID are:

  • Brain shrinkage
  • Accelerated brain aging
  • Excessive activity in the emotional centers of the brain

Getting a functional brain scan with SPECT helps identify COVID-related brain changes.


Serotonin is a neurotransmitter that enables signaling between the body’s nerve cells. This feel-good brain chemical is involved in regulating moods, memory, sleep, stress, cognitive flexibility, sexual desire, and more.

The 2023 study in Cell has linked decreased serotonin levels to the brain fog symptoms seen in post-COVID. Based on a combination of animal studies and human studies, the research found lower levels of serotonin in people with long COVID.

In this study, having decreased serotonin levels post-COVID was also associated with a higher number of neurocognitive symptoms, such as brain fog, memory loss, and confusion.

The research reveals how inflammation that persists post-COVID negatively impacts serotonin levels. According to the paper, inflammation reduces the neurotransmitter in several ways, including:

  • Reducing intestinal absorption of tryptophan, a building block of serotonin
  • Decreasing serotonin storage

The researchers suggest that the decreased levels of serotonin may reduce signaling to a region of the brain called the hippocampus. The hippocampus plays a vital role in memory formation, moods, and learning.

Other research, also published in 2023, has found that COVID-19 triggers functional and structural changes in the hippocampus. Reduced serotonin signaling to this area may be causing these changes.


The researchers of the paper in Cell also investigated the impact of long COVID in stool samples that came from previous studies. They found that in some people with long COVID, traces of the SARS-CoV-2 virus remains in the stool months after the infection.

This indicates that in these individuals, some elements of the virus continue to be stored in the gut. The residual virus, called a viral reservoir, sparks immune system activity that triggers inflammation. It’s this inflammation that decreases the absorption of tryptophan.


Overall, this research has implications for the treatment of long COVID. The scientists suggest that low serotonin levels may be a biomarker for long COVID.

The researchers also sought to determine if boosting serotonin levels could effectively treat symptoms of long COVID. Using animal research, they found that restoring serotonin levels reversed memory loss in mice.

In these trials, they used treatments involving the serotonin precursor tryptophan or selective serotonin reuptake inhibitors (SSRIs), which are common antidepressants. Experts are now exploring if SSRIs may be an effective treatment for long COVID in certain individuals.

This is promising, however, people with long COVID need to be aware that like all antidepressants, SSRIs come with some unwanted side effects. Some of the side effects associated with antidepressants include weight gain, sexual dysfunction (desire, arousal, and ability to orgasm), sleep issues, constipation, dry mouth, and more.

The two most common complaints among patients at Amen Clinics who are taking antidepressants are weight gain and sexual issues. To overcome long COVID brain fog and other symptoms, consider taking a natural approach first.


Because prescription antidepressants are likely to cause side effects, it’s a good idea for people with long COVID to try to boost serotonin naturally. Here are 3 natural ways to increase serotonin levels.

  • Eat foods high in tryptophan. Beef, chicken, turkey, and other animal proteins are excellent sources of tryptophan, a precursor to serotonin.
  • Engage in physical activity. Exercise helps deliver tryptophan to your brain. Some research shows that physical exercise improves serotonin action in the brain.
  • Take supplements that support serotonin. Nutraceuticals that have scientific evidence showing they increase serotonin levels include curcumin, 5-hydroxytryptophan (5-HTP), St. John’s Wort, B vitamins, and magnesium.


Considering the role of inflammation and the gut in the recent findings about long COVID symptoms, it’s also important to reduce inflammation and heal the gut. Natural strategies that may help include:

  • Take omega-3 fatty acids. Having low levels of the omega-3 fatty acids EPA and DHA in the bloodstream is associated with inflammation. And most Americans are low in omega-3. Increase your levels by taking a supplement with EPA and DHA and omega-3-rich foods like salmon, walnuts, and avocados.
  • Reduce intake of omega-6 fatty acids. Store-bought salad dressings, corn, processed meats, and other foods are high in omega-6 fatty acids. Too many Americans eat far more omega-6s compared to omega-3s. You need to flip that equation to reduce inflammation and improve gut health.
  • Eat probiotic foods. Fermented foods, such as kefir and sauerkraut, support gut health.
  • Consume prebiotic foods. Onions, garlic, bananas, and asparagus promote healthy gut bacteria.
  • Practice stress reduction. Chronic stress duels inflammation in the body. Learning to manage stress can help calm inflammation.

Long COVID can be debilitating, so it’s important to be pro-active about your brain health to minimize symptoms. Incorporating these natural brain boosters can help.

Brain fog, memory loss, and other mental health issues related to long COVID can’t wait. At Amen Clinics, we’re here for you. We offer in-clinic brain scanning and appointments, as well as mental telehealth, clinical evaluations, and therapy for adults, teens, children, and couples. Find out more by speaking to a specialist today at 888-288-9834 or visit our contact page here.

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