What Is Serotonin?

Serotonin is a neurotransmitter that sends signals between nerve cells. The main function of serotonin is to stabilize your mood as well as feelings of happiness and well-being. It also plays a role in how brain and nervous system cells communicate, and it has an effect on the digestive system and sleep cycles.

Serotonin can be found in the body’s digestive system, as well as in the central nervous system and blood platelets. The central nervous system consists of the brain and spinal cord. It controls the majority of functions of the body and the mind.

The body produces serotonin by using tryptophan hydroxylase, an amino acid, and creating a chemical reaction that forms the neurotransmitter.Although the body needs serotonin to function, too much or too little can lead to health issues. For example, too little serotonin can cause depression and too much can cause serotonin syndrome, a rare condition that ranges from mild to severe.

Nerve synapse. Computer artwork of a junction, or synapse, between two nerve cells (neurons, blue). As the electrical signal reaches the presynaptic end of a neuron it triggers the release of neurotransmitters across the gap, or synaptic cleft, between the two cells. The neurotransmitters bind to receptors on the postsynaptic membrane, changing the membrane's excitability and triggering an electrical impulse. A network of neurons is in the background. Each neuron consists of a central cell body with many dendrites branching from it.

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Serotonin is responsible for mood regulation. It can reduce feelings of depression and anxiety as well as increase feelings of joy or happiness.

It also plays a vital role in other aspects of our health, including:

  • Sleep: When you sleep, serotonin stimulates areas of the brain that are in control of sleep-wake behavior.
  • Bowel movements: Because most of the body’s serotonin is in the digestive system, it affects how well the bowel functions and plays a role in controlling bowel movements.
  • Blood clotting: When you have a wound, the blood platelets in the body use serotonin to help heal it faster. Serotonin encourages the formation of blood clots and the narrowing of some tiny arteries.
  • Nausea: Nausea is brought on by serotonin. When food that your stomach doesn’t agree with enters the digestive system, the body produces more serotonin. This causes the body to expel food quicker than normal. When the production of serotonin increases in the blood, it causes a reaction in the part of the brain that controls feelings of nausea.
  • Bone health: Research has shown that osteoporosis, which causes bones to become weak or brittle, can be brought on by high levels of serotonin in the body, meaning that having proper levels of this neurotransmitter contributes to the overall health of your bones.
  • Sexual function: When levels of serotonin become too high, it can lead to a decrease in your libido. On the flip side, if levels become too low, you may experience a higher than usual libido or arousal.

Serotonin Deficiency

The causes of serotonin deficiency include:

  • Low levels of tryptophan: If the body does not have enough of this amino acid, it cannot produce enough serotonin.
  • Specific nutrients: Research has shown that vitamin D and omega-3 fatty acids may modulate the creation, release, and function of serotonin. This is because tryptophan relies heavily on vitamin D to do its job. Omega-3s have also been shown to help modulate brain dysfunction because of their effect on the production of serotonin.
  • Not enough serotonin receptors: Having too few serotonin receptors, or receptors that don’t work, could lead to depression and an increased risk of suicide, which are trademark conditions of serotonin deficiency.
  • Stress: Studies have shown that being exposed to high levels of stress in childhood can lead to lower levels of serotonin as an adult. Experiencing traumatic events while the brain is still developing can cause dysregulation of serotonin levels because of the way the protein that transports serotonin is affected.

What Is a Receptor and What Is Its Role in Serotonin Deficiency?

There are two types of receptors: presynaptic and postsynaptic. Presynaptic receptors are designed to regulate the release of neurotransmitters from the synaptic cleft. The synaptic cleft is the space between neurons that allows the exchange of information to occur.

Postsynaptic receptors are designed to receive the signal from the presynaptic receptor. In the event that these receptors are not functioning properly or there are not enough of them, low serotonin levels can result.


Because serotonin affects many bodily processes, having inadequate amounts of the neurotransmitter can lead to both psychological and physiological issues. Some symptoms that are associated with serotonin deficiency can be grouped into the following categories:

  • Psychological: Anxiety and panic disorder, depression, aggression, poor impulse control, insomnia, irritability, low self-esteem, eating disorders, obsessive-compulsive disorder (OCD)
  • Cognitive: Poor memory, fatigue
  • Physiological: Craving carbohydrates, unintended weight gain, nausea, digestive issues, poor appetite

Low levels of serotonin have also been associated with the development of certain chronic diseases, such as Alzheimer’s disease and Parkinson’s disease. The normal range of serotonin in the blood is roughly 101–283 nanograms per milliliter.


Treatments for low serotonin levels can include:

  • Medications: Selective serotonin reuptake inhibitors (SSRIs) are a type of antidepressant prescribed to help the body use serotonin better. They stop presynaptic receptors from picking up the serotonin before the postsynaptic receptors have a chance to bind to it. The medications allow serotonin levels to increase.
  • Light therapy: Light therapy is when people expose themselves to bright lights often. The light can be from the sun or a lightbox. Research has shown that being exposed to more light may increase serotonin levels in the brain.
  • Lifestyle changes: Lifestyle changes can help to increase levels of serotonin. When it comes to diet, research shows that eating foods high in tryptophan can lead to an increase in serotonin.Exercising regularly also can help boost serotonin levels. Aerobic exercise is particularly helpful. Research has also found that practicing meditation can help to boost serotonin in the brain.

High Serotonin

Serotonin levels that are too high can be dangerous. In some cases, high levels of serotonin in the blood can be caused by a condition known as carcinoid syndrome. The syndrome is caused by a tumor that produces too much serotonin and can cause symptoms like:

  • Flushed skin or redness
  • Facial skin lesions
  • Gastrointestinal issues, such as frequent diarrhea and abdominal cramps
  • Asthma-like symptoms, such as wheezing
  • Rapid heartbeat
  • Dehydration
  • Weakness
  • Muscle and joint pain

Another syndrome, known as serotonin syndrome, can occur if levels of the neurotransmitter become dangerously high.

Serotonin Syndrome

Serotonin syndrome is characterized by markedly high levels of serotonin in the body. It can be life-threatening and requires emergency medical assistance. Common causes of serotonin syndrome include:

  • Medications that increase serotonin levels, such as SSRIs
  • Medications that treat pain
  • Over-the-counter cold medicines and cough suppressants containing dextromethorphan
  • Migraine medications, such as triptans
  • Medications used to treat human immunodeficiency virus (HIV), which can lead to AIDS
  • Antinausea medications like metoclopramide and ondansetron
  • Supplements, including ginseng and Saint-John's-wort
  • Illicit drugs like ecstasy, cocaine, or LSD

People with serotonin syndrome will often suffer from various symptoms that can be mild or severe. Mild symptoms may include:

  • Nervousness
  • Insomnia
  • Nausea
  • Diarrhea
  • Tremors
  • Dilated pupils

Moderate symptoms can include:

  • Hyperreflexia (hyperactive reflexes)
  • Sweating
  • Agitation and restlessness
  • Inducible clonus (involuntary muscle contractions)
  • Side-to-side eye movements

In severe cases, people may have a high fever, confusion or delirium, sustained clonus or rigidity, rhabdomyolysis (the breaking down of damaged muscle), or death.

If you experience any of the above symptoms and have just recently started or increased your dosage of a medication that can affect serotonin levels, seek medical attention right away.


People with serotonin syndrome will likely need to be hospitalized for a minimum of 24 hours for observation. If the case is mild and caused by a medication, simply stopping the medication or changing the dosage can relieve the symptoms and restore normal serotonin levels.

Medications that stop the body from producing serotonin may be prescribed to help relieve symptoms and keep the condition from worsening. Some medications that are often used during hospitalization include: 

  • Benzodiazepines: These are used to help decrease agitation, seizure-like movements of the body, and muscle stiffness. 
  • Cyproheptadine: This type of medication is used to block the production of serotonin.

In severe cases, as is often the case with serotonin syndrome, hospitalization for longer than 24 hours may be needed so that a person can be monitored closely for changing or worsening symptoms. Since serotonin syndrome can be life-threatening, medical attention is required as soon as possible.

While in the hospital, patients with serotonin syndrome may have to take medications that paralyze their muscles and may also need to be put on a temporary breathing tube and breathing machine to prevent muscle damage. 

How to Increase Serotonin Naturally

If you have or suspect you have low levels of serotonin, there are ways you can boost your levels naturally.


Since tryptophan is the precursor to serotonin, eating a diet with foods that are either high in the amino acid or could help boost the concentration of it in your blood could help increase levels naturally. Eggs are one food that can help boost levels of tryptophan. Other foods that you can include in your diet include tofu, salmon, turkey, nuts and seeds, and cheese. 

Increasing your intake of carbohydrates may also increase your levels of tryptophan. Studies have shown that an increase in carb intake while eating foods high in tryptophan can help tryptophan reach the brain easier.


Certain dietary supplements can help restore normal serotonin levels naturally, including:

  • Tryptophan supplements: If you can’t get enough tryptophan through food, supplements are available to help increase your intake of this amino acid.
  • S-adenosylmethionine: This is the supplement version of the chemical compound that is found naturally in the body. It is used in the body in a process known as methylation, which is the chemical reaction that goes on in all cells of the body to help promote proper functioning. Methylation is one of the final steps that occur in the production of serotonin. For serotonin production to be optimal, the body must have enough S-adenosylmethionine.
  • 5-HTP: This is the supplement version of the natural amino acid found in your body.
  • Probiotics: Studies have shown that taking probiotics may help increase levels of tryptophan in the blood.

Light Exposure

Light exposure, also known as light therapy, can improve serotonin levels and decrease symptoms of depression. Research has shown that exposure to sunlight may help the body synthesize serotonin through the skin.


Getting enough exercise is important for overall health, but it can also boost serotonin levels naturally. Exercise triggers the release of tryptophan into the blood, driving serotonin production. There are many types of exercise that can help trigger this response, such as swimming, jogging, hiking, or dancing.


Massage therapy has been shown to help increase serotonin levels while decreasing levels of the stress hormone known as cortisol.

Frequently Asked Questions

How common is serotonin syndrome?

Although the prevalence of serotonin syndrome isn't known, one small study looked at how often patients experienced symptoms of the syndrome and found that roughly 7.8% of the 309 intensive care unit (ICU) patients had some symptoms of serotonin syndrome. It's important to note that this is not a typical patient population.

When is serotonin released?

The release of serotonin can occur at various parts of the day and during different activities. Some research suggests that serotonin can be released when the body becomes nauseated to help remove bad food from the body. Massage therapy has also been shown to trigger the release of serotonin, as well as spending time in sunlight or exercising.

Although data surrounding the time of day that you experience the highest release of serotonin is scarce, one study published in 2009 found that levels of serotonin in rats that were fed tryptophan orally are highest between the hours of 9 p.m. and 11 p.m.However, elevated levels of serotonin may be driven by the increase in tryptophan.

How long does it take for serotonin to replenish?

There is no set time for when serotonin levels are replenished. This is because brain chemistry varies from person to person. For mild cases of serotonin deficiency, levels may be replenished quickly, while it may take longer for others.


Serotonin is a neurotransmitter that plays an important role in regulating mood, sleep, and your digestive system. High or low levels of serotonin can lead to problems. However, both can be treated with medications and lifestyle changes. There are also natural ways you may boost your serotonin levels.

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