Serotonin Deficiency: Signs, Symptoms, Solutions

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Last updated February 14, 2024.
Edited and medically reviewed by Patrick Alban, DC. Written by Deane Alban.

Serotonin deficiency can be a cause of depression, anxiety, and more. Increase your serotonin level naturally with diet, supplements, and lifestyle choices.

If you struggle with depression, anxiety, or the “blues,” you may have a serotonin deficiency.

Serotonin is the main neurotransmitter associated with feelings of happiness, relaxation, and self-confidence.

Low serotonin levels are believed to be at least partly responsible for our current epidemics of depression and anxiety.

But antidepressant drugs aren’t the only way to increase serotonin.

Here’s what you can do to increase your serotonin level naturally with diet, supplements, and lifestyle choices.

What Is Serotonin? What Does It Do?

Neurotransmitters are chemicals used by brain cells to communicate with each other.

And serotonin is one of the most important neurotransmitters.

Serotonin exhibits a wide range of functions in both the brain and elsewhere in the body, especially the central nervous system and the gastrointestinal tract.

The first known function of serotonin was controlling blood vessel constriction. 

But it is much better known as the “happy molecule” for the important role it plays in positive mood.

" Serotonin synthesis and mood is a two-way conversation. Just as serotonin can affect your thoughts, your thoughts can affect your serotonin levels.

Most brain cells are affected directly or indirectly by serotonin whereby it regulates mood, social behavior, libido, sleep, memory, and learning.

The advent of prescription antidepressants like Prozac and Zoloft turned serotonin into a household word.

These drugs are selective serotonin reuptake inhibitors (SSRIs) which are thought to work by increasing serotonin levels.

While serotonin is almost always associated with brain function, mood, and mental well-being, surprisingly 95% of our serotonin is manufactured in the intestines, not the brain. 

In fact, this “second brain” in our gut contains 100 million nerve cells, more than in either the spinal cord or the peripheral nervous system. 

Researchers are still unclear as to why there is so much serotonin activity in the intestines. 


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It seems that serotonin facilitates communication between the gut and the brain, but serotonin used by the brain must be produced there since serotonin created in the gut is unable to pass through the brain’s protective filter

Because so much serotonin resides outside of the brain, some experts consider serotonin a hormone as well as a neurotransmitter.

What “Serotonin Deficiency” Means

A serotonin deficiency would seem to mean that simply too little serotonin is being made, but that is not always the case.

Here are a few of the other reasons brain serotonin levels can be low: 

  • The brain has too few serotonin receptors or these receptors aren’t working as well as they should.
  • Serotonin is broken down too soon or not properly recirculated.
  • Serotonin formation is inhibited.

We’ll use the terms serotonin deficiency and low serotonin level as shortcuts to mean that one or more of these processes is taking place.

Low Serotonin Symptoms

There is no reliable way to quantify a serotonin deficiency since there is currently no reliable way to measure serotonin in the brain.

And while we can measure serotonin urine or blood levels, there is no evidence that this reflects what is going on in the brain. 

This is why taking note of signs and symptoms is a better indicator of a neurotransmitter imbalance than blood or urine tests.

Depression is the most widely known sign of low serotonin, but it is certainly not the only one.

Numerous other disorders are linked to low serotonin, including: 

Not all serotonin deficiency symptoms are this obvious.

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A low serotonin level can also be associated with vague symptoms like these:

  • anger
  • binge eating and carbohydrate cravings
  • constipation
  • digestive complaints
  • feeling glum from lack of sunlight
  • feeling overly dependent on others
  • feeling overwhelmed
  • hypervigilance
  • insomnia
  • joylessness
  • low self-esteem
  • migraines
  • pain sensitivity
  • poor cognitive function
  • tinnitus

Low serotonin impacts your overall health and even your longevity

Serotonin deficiency increases the risk of stroke, dementia, and Alzheimer’s

It can contribute to the severity of symptoms of asthma, fibromyalgia, migraines, and irritable bowel syndrome (IBS). 

How Low Serotonin Symptoms Are Different in Men and Women

Interestingly, low serotonin symptoms are expressed somewhat differently in men and women.

Women are twice as likely to experience depression, anxiety, and other mood disorders than men. 

They’re also more likely to exhibit carbohydrate cravings, binge eating, and subsequent weight gain.

Overeating carbs is a way of self-medicating to raise serotonin levels. 

Men with low serotonin, on the other hand, are more prone to alcoholism, ADHD, and impulse control disorders

Serotonin Deficiency Causes

According to Harvard researcher Datis Kharrazian, PhD, DHSc, author of Why Isn’t My Brain Working?, the long-term use of SSRIs, blood sugar imbalances, adrenal fatigue, nutritional deficiencies, hormone imbalances, and birth control pills can be underlying causes of serotonin deficiency.


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But, more commonly, serotonin deficiency is related to unhealthy lifestyle habits such as poor diet, excessive stress, artificial sweeteners, alcohol or caffeine consumption, and a lack of sunlight

The Link Between Low Serotonin and Depression

No one knows for sure what causes depression, but the serotonin theory of depression is currently the prevailing model.

This is why most antidepressants, notably selective serotonin reuptake inhibitors (SSRIs) such as Prozac and Zoloft, are designed to increase serotonin levels.

SSRIs are believed to improve mood by blocking brain receptors that reabsorb serotonin, leaving more serotonin available for use.

But it’s not fully understood exactly how SSRIs work

Some users find them to be life-altering, but many who try them find that they don’t help

One possible explanation is that since there are several mechanisms that can lead to low serotonin levels, not everyone will respond similarly to any one treatment.

Another theory growing in popularity is that inflammation, not neurotransmitter imbalance, is the root cause of depression.

Interestingly, SSRIs exhibit potent anti-inflammatory properties which may be a reason they work for some people. 

Another possible reason SSRIs don’t always work is that not all depression is caused by low serotonin.

For many, dopamine deficiency can be the underlying cause instead.

Lastly, it’s not really known whether a low serotonin level causes depression or whether depression causes serotonin levels to drop.

It’s confusing to say the least!

It may be that the ultimate cause of depression will be found to be multifactorial and not the same for everyone.

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But, in the meantime, if you don’t want to take SSRIs or haven’t found them helpful, you can try increasing your serotonin level naturally with diet, supplements, and certain healthy lifestyle choices.

An important reminder: Do not stop taking any medications without talking to your doctor first.

Serotonin Deficiency and Anxiety

Serotonin deficiency can also cause anxiety, either with or without accompanying depression.

Oddly, having anxiety along with depression is information you can put to good use.

This is a sign that your depression is likely to be caused by low serotonin.

When depression is related to low dopamine, it is usually accompanied by lethargy rather than anxiety. 

SSRIs are often used to treat anxiety disorders — generalized anxiety disorder, panic disorder, and obsessive-compulsive disorder (OCD) — that are linked to low serotonin levels.

Low Serotonin and Insomnia

Sleep problems of all kinds — the inability to fall asleep, sleep deeply, or stay asleep — can be due to a lack of serotonin.

Serotonin is a precursor to melatonin, the hormone responsible for managing our biological clock. 

Of course, many causes of insomnia have nothing to do with serotonin.

But, according to Dr. Kharrazian, if melatonin supplements help you sleep, that’s an indication that your insomnia is serotonin-related.

The Surprising Way to Increase Serotonin With Food

One seemingly obvious way to increase serotonin would be to eat foods that contain it.

While some foods such as walnuts, hickory nuts, bananas, pineapple, kiwis, plums, and tomatoes do contain serotonin, eating them is not an effective strategy since the serotonin in these foods does not enter the brain. 

Another option would be to eat foods containing serotonin’s precursor, tryptophan.

Tryptophan is an amino acid found in most protein food sources.

However, trying to raise serotonin levels by eating tryptophan presents an interesting paradox.

Protein blocks serotonin synthesis and, consequently, levels of both tryptophan and serotonin actually drop after eating protein. 

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There are only a handful of foods known to increase serotonin naturally by other mechanisms:  

It’s not a coincidence that people binge on sweet or carbohydrate-rich “comfort foods” when they’re feeling down.

A blast of refined carbohydrates is a quick way to raise serotonin levels. 

But sugar also triggers a boost of the stress hormone cortisol that can last up to five hours. 

The most reliable way to raise your serotonin level with food is to occasionally eat healthy carbohydrates separately from protein.

Supplements for Serotonin Deficiency

There are many kinds of natural serotonin boosters — herbs, vitamins, minerals, and more.

Two of the most popular serotonin supplements are the amino acids tryptophan and 5-HTP.


Tryptophan is a rare case where supplements work better than foods containing tryptophan. 

As mentioned above, eating protein decreases both tryptophan and serotonin levels.

But tryptophan supplements provide a neat workaround to this dilemma.

They increase brain levels of serotonin while bypassing protein’s negative effect on serotonin formation.


5-HTP is converted into both serotonin and melatonin, making it popular for those with both depression and insomnia.

But this is not our favorite serotonin-boosting supplement.

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5-HTP has some serious downsides.

It’s not intended for long-term use and often quits working after a few months. 

It should never be mixed with SSRIs or other antidepressant medications. 

Additionally, it should not be mixed with herbs that are natural relaxants or supplements that work by increasing serotonin levels.

Other Serotonin-boosting Supplements

Other supplements that increase serotonin naturally include:

  • B complex vitamins
  • bacopa
  • curcumin
  • l-theanine
  • magnesium
  • omega-3 essential fatty acids
  • probiotics
  • Rhodiola rosea
  • SAM-e

Just as no single antidepressant works for everyone, no one supplement does either.

You can expect to do some trial and error testing before hitting on a winning combination that works for you.

Increasing Serotonin With Lifestyle Choices

Some of the best ways to increase serotonin levels are not substances that you ingest, but activities that you do.

Be Social

Simply spending time with friends can increase serotonin levels. 


Physical exercise can improve your mood by increasing the levels of numerous feel-good brain chemicals, including serotonin. 

Exercise has been found to work even better for depression, especially if you do it outside

Compared to indoor exercise, exercising outdoors increases vitality, enthusiasm, pleasure, and self-esteem while lowering tension, depression, and fatigue. 

Even if you aren’t exercising, simply being in nature quiets the mind and enhances mental well-being. 

Get in the Sun

Sunlight boosts serotonin and provides the additional benefit of creating vitamin D, a known mood booster. 

If sunlight isn’t available, selective exposure to bright artificial light can also help. 

But limit your artificial light exposure at night, especially the blue light from your electronic devices.

The blue light emitted from your screens can reduce melatonin levels by 22%

Play in the Dirt

Dirt has been called the “new Prozac.”

Why? Because exposure to microbes found in soil increases serotonin levels. 

This may be a reason that so many people feel happy when they garden.

Get a Massage

Massage isn’t just pleasant and relaxing, it’s genuinely therapeutic.

It can increase serotonin and dopamine while reducing the stress hormone cortisol. 

It also changes your brainwave activity to make you feel more alert. 

Mind Your Thinking

Learn to monitor your thoughts.

Serotonin synthesis and mood is a two-way conversation.

Just as serotonin can affect your thoughts, your thoughts can affect your serotonin levels. 

Focus on happy memories.

Nip negative thinking and cognitive distortions in the bud. 

Positive self-talk and uplifting thoughts can promote serotonin synthesis while decreasing cortisol. 


Unfortunately, controlling the “random thought generator” in your head is not easy, but meditation can help.

Meditation is a proven technique for gaining control of your thoughts.

It also increases your resilience to stress, while boosting serotonin. 

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