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What is Serotonin Deficiency & How is it Treated? | Causes, Symptoms of Serotonin Deficiency

Serotonin deficiency is a condition that occurs when there is not enough serotonin activity in the body. Serotonin is an important neurotransmitter that is responsible for regulating some of the most critical functions in the body. While most people are aware of serotonin’s role in mood regulation, the chemical is also responsible for your appetite, sleep cycle, and digestion, as well as other physical processes. Serotonin deficiency can cause a wide variety of physical and psychological symptoms. Here’s everything you need to know about serotonin deficiency.

What is Serotonin Deficiency?

Serotonin is a neurotransmitter in the brain that is responsible for regulating many of the body’s most important functions.(1,2,3) Apart from regulating your mood, serotonin also has an effect on your appetite, digestion, and your sleep cycle, along with other physical processes. Nearly 95 percent of the serotonin in the body is manufactured in the lining of the gastrointestinal tract, where it has the responsibility of regulating the movement of the intestines. The other five percent is manufactured in the brainstem, from where it transmits signals between the nerve cells in the brain.(4,5)

Serotonin deficiency is a condition that occurs when there is not enough serotonin activity in the body. This can happen for a variety of reasons and is typically associated with a wide variety of psychological and physical symptoms.(6) However, the exact role of serotonin in these symptoms is not clearly understood, particularly the psychological symptoms. For example, the connection between serotonin and depression is still hotly debated.(7) Nevertheless, the one thing that all medical experts agree upon is that the function of serotonin is much more complex than earlier believed.

What are the Symptoms of Serotonin Deficiency?

Serotonin deficiency is known to cause a wide variety of physical and psychological symptoms. Some of the psychological symptoms of the condition include:(8,9,10)

  • Depressed mood
  • Anxiety
  • Insomnia
  • Aggression
  • Impulsive behavior
  • Irritability
  • Poor memory
  • Poor appetite
  • Low self-esteem

Additionally, low levels of serotonin in the body is also believed to be connected with various psychological conditions, including:

Doctors still do not clearly understand the exact role serotonin plays in these psychological symptoms and conditions. At the same time, serotonin deficiency seems to affect men and women in different ways.

A 2007 study discovered that reduced levels of serotonin in the brain could cause depression and other related mood changes in women. Male participants of the study, however, were found to become more impulsive but did not report any changes in their mood.(11)

Another more recent study found that serotonin deficiency can affect mood differently in those who have previously experienced depression as compared to people who have never had depression. People who have never had depression are not likely to become significantly depressed when they experience serotonin deficiency.(12)

Serotonin deficiency is also known to cause a wide variety of physical symptoms as well, considering the important role it plays in many of the body’s critical functions. Here are some of the physical symptoms caused by serotonin deficiency:

What are the Causes of Serotonin Deficiency?

While researchers are still not sure about the exact cause of serotonin deficiency, it has also been observed that some people simply tend to produce less serotonin than others.

Some of the other likely causes of serotonin deficiency include:

  • Serotonin being absorbed or breaking down too soon.
  • Having lesser serotonin receptors in the body
  • Having serotonin receptors that do not function properly and are not able to receive serotonin effectively.
  • Having low levels of vitamin D, vitamin B6, omega-3 fatty acids, or L-tryptophan – all these are needed for the body to produce serotonin.(15,16)

Apart from these, it is also believed that various life experiences may also play a role in who gets serotonin deficiency.

For example, a study found that participants who had experienced any form of abuse in childhood naturally had lower brain serotonin transporter binding potential than people who were not abused in childhood. This 2009 study demonstrated that people who had been abused at some point in their lives had naturally lower serotonin activity.(17,18)

How is Serotonin Deficiency Diagnosed?

It can be challenging to diagnose serotonin deficiency because there is no way to precisely test the levels of serotonin present in the brain, and there is also a lack of specific diagnostic criteria.(19)

Even though there is a test that can measure the level of serotonin in the bloodstream, but it is usually only used to check for the presence of any serotonin-producing tumors outside the brain. Also, the blood serotonin levels don’t necessarily indicate what are the levels of the chemical inside your brain.

It is best to stay away from the various neurotransmitter urine tests that are sold online. In 2010, a study debunked various claims that these online tests can help in the diagnosis of serotonin deficiency in the brain.(20)

The brain is protected by a membrane known as the blood-brain barrier (BBB), which is a semi-permeable membrane that allows some things to get through while blocking others. Serotonin is one such substance that is unable to cross through the blood-brain serotonin.(21)

This means that the serotonin in your brain has to be produced in the brainstem. This, therefore, makes the serotonin measurement in your blood and urine an unreliable source to determine the serotonin amount in the brain.

So if you think you are experiencing the symptoms of a serotonin deficiency, it is best to keep track of your symptoms for at least a couple of weeks and discuss with your doctor about how to narrow down your diagnosis.

Treatment of Serotonin Deficiency

Regardless of the underlying cause of your serotonin deficiency, there are various effective ways of increasing serotonin functioning, both in the body and the brain. Here are some of the treatment options for serotonin deficiency.

Selective Serotonin Reuptake Inhibitors

Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are used to treat depression. These antidepressant medications also help your body use the available serotonin more effectively.(22) These drugs work by inhibiting the serotonin reuptake by the presynaptic receptors. This allows for serotonin to become more available to be able to bind to the postsynaptic receptors. This causes more serotonin in the synapses between the ends of neurons, thus increasing the amount of serotonin available for use.

These medications do not help produce more serotonin, but instead, they help the body use what it already has more effectively.

Some of the commonly prescribed selective serotonin reuptake inhibitors include:

  • Sertraline (brand name Zoloft)(23)
  • Fluoxetine (brand names Prozac, Sarafem)(24)
  • Citalopram (brand name Celexa)
  • Paroxetine (brand name Paxil)
  • Escitalopram (brand name Lexapro)(25)

Natural Remedies to Increase Serotonin

Just like any other type of medication, selective serotonin reuptake inhibitors are not effective for everyone. In some cases, this class of drugs can also cause a variety of adverse side effects.(26) In case these medications are not recommended for you, there are various other natural remedies you can try that are quite effective. These include:

Exercise: Many studies have shown that physical activity helps improve the levels of brain serotonin as it increases both the release and production of serotonin in the brain.(27) Walking, swimming or running are believed to be the most effective types of aerobic exercises that help boost your serotonin levels.

Mood induction: This method involves intentionally creating a happy mood by indulging in something you love doing or thinking about things that make you feel happy. A 2007 study discovered that mood induction helped increase serotonin levels in the brain.(28)

Diet: Increasing the intake of foods that contain nutrients your body needs to naturally increase the production of serotonin can help. These include foods that are rich in:

  • Tryptophan
  • Vitamin D
  • Omega-3 fatty acids
  • B vitamins

Exposure to bright light: Many studies have found that exposure to bright light, either from a lightbox or the sun, can help boost the levels of serotonin in the brain.(29)


Not having enough serotonin in the body can have a wide variety of effects on your physical and psychological health. Nevertheless, there are still many unanswered questions about how serotonin exactly works in the brain and the body, due to which the condition of serotonin deficiency also remains poorly understood.

If you think you may have serotonin efficiency, it is best to discuss with your doctor to get a better understanding of what underlying condition could be causing your symptoms. You can also try some simple but effective, natural remedies to increase serotonin naturally and checking if your symptoms improve.


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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:February 13, 2021

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