Serotonin is an essential hormone and neurotransmitter that plays a role in a wide range of bodily functions. Various conditions can occur with low serotonin activity, including depression and anxiety.

Researchers have linked serotonin deficiency with depression and potentially a wide range of other conditions.

Drugs that boost serotonin levels or activity, such as selective serotonin reuptake inhibitors (SSRIs), can help manage depression and anxiety, as well as migraine and some other conditions.

The serotonergic system is highly complex, and scientists do not yet understand precisely how it works.

In time, a better understanding of serotonin functioning may lead to treatments for various conditions linked to low serotonin levels. For now, however, blood serotonin levels are not usually a reliable indicator of any specific disease.

In this article, learn about what a person may notice if serotonin levels are low, why it happens, and how to address it.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Serotonin (5-HT) is a hormone. As a neurotransmitter, it is involved in the transmission of messages in the central nervous system (CNS). However, it has other functions, too.

Serotonin is involved in nearly every part of the brain. A serotonin imbalance has been linked to various mental and physical health problems.

The body uses an amino acid, tryptophan, to synthesize or produce serotonin. Serotonin is synthesized in the CNS and stored mainly in the gastrointestinal tract, though also in the CNS and platelets.

Serotonin’s function in the body is part of a highly complex process.

It contributes to a wide range of functions in the CNS and throughout the body, such as:

Much remains unknown about serotonin and how it works.

However, experts have linked low serotonin activity with a range of psychiatric problems, including depression, anxiety, attention deficit hyperactivity disorder (ADHD), and post-traumatic stress disorder (PTSD).

Serotonin syndrome, also called serotonin toxicity, can result if too much serotonin is active in the nervous system. This is a life threatening condition that usually results from medication use, the use of recreational drugs, or drug interactions.

Symptoms include:

  • tremors
  • a rapid heart rate
  • muscle rigidity
  • agitation

A person with serotonin syndrome needs immediate medical help.

SSRIs are prescription drugs that can help reduce symptoms of some physical and mental health conditions. These drugs boost serotonin concentrations or enhance the body’s use of serotonin.

These drugs can improve mood problems or reduce anxiety for some people with a diagnosed mental health condition.

Other ways of maintaining healthy serotonin levels include exercise, stress management techniques, and possibly some foods.

Learn how to increase serotonin levels.

Serotonin helps regulate a wide range of bodily functions, including:

  • sleep
  • appetite
  • mood
  • learning and memory

However, since its role in the body is part of a complex process, it can be difficult to determine whether low serotonin or something else is causing a specific symptom.

The sections below will look at some possible symptoms of low serotonin levels.

Psychological symptoms

Mental health symptoms are among the most common manifestations of low serotonin activity.

Here are some symptoms that may occur:

Mood changes

Serotonin helps regulate mood. People who feel unusually irritable or down for no apparent reason may have low serotonin activity.

Depression

Feelings of sadness, hopelessness, and anger, as well as chronic fatigue and thoughts of suicide, may indicate depression.

Anxiety

A person with anxiety may worry excessively about specific issues or often experience general or non-specific feelings of anxiety.

Memory issues

People with dementia may also have low serotonin activity. Experts believe there is a link between depression and the risk of dementia. However, they do not yet know what links them.

Sleep problems

Serotonin helps regulate sleep. Sleep problems may occur when there is an imbalance of serotonin.

Sexual function

Serotonin appears to affect sexual function. Medications that affect serotonin levels can have a complex effect on sexual function and drive.

Cognition and attention

Serotonin is one of many neurotransmitters that support the ability to concentrate and learn new information.

Some experts have suggested that people with dementia may experience changes in serotonin function. More research is needed to determine whether treatments that increase serotonin activity could affect cognitive functioning in dementia.

In time, researchers may discover other ways low serotonin activity affects mental health.

Role in physical health and possible symptoms

Serotonin appears to play a role in the nervous system. As such, it will affect the overall functioning of the body.

Gastrointestinal symptoms

Serotonin is one of a group of hormones that help balance digestive processes and regulate bowel function and movements. Serotonin also regulates a person’s appetite.

Pain perception

Some people who experience psychological distress may have physical symptoms, such as chronic pain, with no clear physical origin. A 2019 study suggests that disruptions in the serotonin pathway may contribute.

Movement issues

Experts believe boosting serotonin activity may help reduce resting tremors in Parkinson’s disease, suggesting low serotonin activity may play a role in worsening symptoms.

Blood clotting

Serotonin plays a role in blood clotting. High serotonin activity may promote the narrowing of blood vessels. However, it is unclear whether low activity would lead to excessive bleeding due to clotting disorders.

Wound healing

There is some evidence that serotonin plays a role in wound healing by increasing the migration of cells to areas in need of regeneration.

While this suggests serotonin could play a role in healing wounds, there is no evidence that low serotonin levels affect the body’s ability to heal.

Inflammation and immunity

Scientists say serotonin plays a crucial role in the immune system, and many immune cells contribute to serotonin-related processes. Some researchers are investigating whether serotonin may provide a link between the immune system and the CNS.

Bone density

Some mouse studies have suggested that low serotonin activity in some parts of the body may increase the risk of low bone density. However, more research is needed to see if this applies to humans.

Migraine

Serotonin plays a key role in the development of migraine. However, scientists have not yet identified the link.

One theory suggests that serotonin levels are likely to be high between attacks and low during an attack, indicating a link between low serotonin levels and migraine symptoms. However, a 2018 study concluded that the opposite may be true.

Pain

Various neurotransmitters play a role in the experience of pain, including serotonin.

In addition to migraine, problems with the serotonergic system have been linked to painful conditions such as irritable bowel syndrome (IBS) and fibromyalgia.

Healthcare professionals do not fully understand why some people have low serotonin activity.

However, here are some factors that may contribute:

  • genetic factors
  • age-related health and brain changes
  • chronic stress
  • a lack of exposure to natural light
  • lack of physical activity
  • chronic pain

However, in many cases, there is no clear cause.

Learn about tryptophan supplements.

Doctors usually diagnose low serotonin based on symptoms, not blood levels of serotonin.

SSRIs appear to work by increasing serotonin activity rather than serotonin levels in the blood. For this reason, measuring serotonin levels is unlikely to be helpful.

A doctor may recommend a test if they suspect a carcinoid tumor.

These tumors start in certain body cells and can appear in the lungs, stomach, small intestine, rectum, and appendix. They produce tryptophan, which the body can convert into serotonin. However, the doctor is more likely to test for high levels of tryptophan than serotonin.

A doctor may prescribe medication to maintain healthy serotonin levels. However, non-drug remedies can also help.

Medications

Medications can boost serotonin activity.

These drugs include the following antidepressants:

  • SSRIs, such as escitalopram (Cipralex) and fluoxetine (Prozac)
  • selective norepinephrine reuptake inhibitors (SNRIs), such as duloxetine (Cymbalta) and venlafaxine (Effexor XR)
  • monoamine oxidase inhibitors (MAOIs), such as isocarboxazid (Marplan) and phenelzine (Nardil)

They work in different ways. Doctors often prescribe SSRIs and SNRIs than the older style MAOIs, which are more likely to have adverse effects.

SSRIs have FDA approval to treat:

Doctors may also prescribe SSRIs off-label to treat the following:

Many factors can contribute to these conditions. However, if symptoms improve with SSRIs, it suggests that low levels of serotonin are contributing in some way to symptoms.

Learn about the differences between SSRIs and SNRIs.

Psychotherapy

Psychotherapy can help ease the symptoms of various mental health conditions, including anxiety, depression, insomnia, and trauma.

Several studies suggest that therapy may regulate serotonin activity. For example, one 2012 study found that therapy increased serotonin receptors in the brains of people with major depression.

Learn about different types of therapy.

Stress management techniques

Chronic stress can affect how the brain processes or produces serotonin and may lead to a wide range of symptoms, such as mood changes, difficulty thinking, and changes in body temperature.

Finding ways to manage stress may help keep serotonin neurotransmission stable, and this may help regulate mood.

Learn about ways to manage stress.

Light therapy

Bright light may help treat seasonal affective disorder (SAD), and some research suggests it may also boost serotonin function and prevent low mood in people with SAD.

A 2015 study looked at the effect of light therapy on 10 females with chronic headache due to temporomandibular joint disorders. Three days after treatment, serotonin levels were significantly higher, and pain levels were 64% lower.

Exercise

Research suggests exercise can help raise serotonin levels, boost mood, and manage depression.

Diet

Tryptophan — present in foods such as salmon and poultry — helps the body produce serotonin.

Some scientists have suggested that eating foods containing tryptophan could increase the body’s potential to produce serotonin, and so boost mood and thinking. However, more research is needed.

Foods containing tryptophan include:

  • dairy products
  • meats, including turkey
  • seeds
  • fruits

Learn about foods that contain tryptophan.

Serotonin helps the body regulate many functions, including mood.

Changes in serotonin function can occur with mental health symptoms, and medications that boost serotonin activity can help people with depression and anxiety. This suggests a link between serotonin and mental health.

Low serotonin can also occur with physical symptoms, such as erectile dysfunction and chronic pain, which can also affect a person’s mental health.

Serotonin function may vary between males and females. Estrogen, which is higher in females, can affect the production, use, and degradation of serotonin.

According to the authors of a 2019 review, animal studies have suggested that boosting estrogen levels may lead to an increase in serotonin.

However, it may depend on how long estrogen treatment lasts. In one study, serotonin levels fell as estrogen therapy progressed.

Serotonin plays a role in many aspects of health, and a deficiency could occur with a wide range of medical conditions.

Moreover, not everyone with symptoms of depression or other mental health conditions will have low serotonin. Symptoms alone will not show if a person has low serotonin activity.

A person should see a doctor for:

  • depression or anxiety that does not improve with self-care
  • memory loss
  • movement issues
  • changes in sleep, appetite, or digestion
  • any side effects associated with serotonin-related treatments
  • signs of serotonin toxicity, especially after taking prescription or recreational drugs

Here are some answers to questions people often ask about serotonin deficiency.

How do you know if your serotonin is low?

It is not possible for an individual to know if their serotonin levels are low. However, people who see a doctor with persistent symptoms of depression may benefit from drugs and lifestyle measures that regulate serotonin function.

How can I raise serotonin levels naturally?

Exercise and stress management can help prevent or manage conditions that involve low serotonin activity and may increase serotonin activity.

Eating foods that contain tryptophan provides more of the substance the body needs to produce serotonin. People with low serotonin activity due to SAD may benefit from light therapy.

How do I talk with my doctor about this?

Anyone with concerns that they may have depression, anxiety, or any other condition, regardless of whether it affects serotonin function, should speak with a doctor about their symptoms and ask about treatment options.

Serotonin contributes to a wide range of bodily functions, and many aspects of well-being may depend on a balance in serotonin activity.

In most cases, however, measuring serotonin levels is not a way to diagnose a health condition. A doctor will likely focus on symptoms, they may carry out other tests, and then they will treat the condition they diagnose.

Some conditions may respond well to treatments that boost serotonin activity in the body. In this case, a person may understand that they previously had a serotonin imbalance.