Serotonin Deficiency: Signs, Symptoms, Solutions

Edited and medically reviewed by Patrick Alban, DC | Written by Deane Alban

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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 the “blues,” depression or anxiety, 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.

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?

Serotonin is one of the most important neurotransmitters — chemicals used by brain cells to communicate with each other.

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

The first known function of serotonin was controlling blood vessel constriction. (1)

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

Most brain cells are affected directly or indirectly by serotonin where 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 believed 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. (2)

In fact, this “second brain” in our gut contains 100 million neurons, more than in either the spinal cord or the peripheral nervous system. (3)

Researchers are still unclear as to why there is so much serotonin activity in the intestines. (4)

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. (56)

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

What a “Serotonin Deficiency” Means

A serotonin deficiency sounds like you simply make too little of it, but that is not always the case.

Here are a few of the other reasons brain serotonin can be low: (7)

  • Your 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 that mean that one or more of these processes is taking place.


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Low Serotonin Symptoms

There is no reliable way to quantify a serotonin deficiency since there is currently no 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. (8)

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: (91011121314, 151617)

  • anxiety and panic disorders
  • attention disorders
  • eating disorders
  • multiple sclerosis
  • obsessive-compulsive disorder
  • post-traumatic stress disorder
  • seasonal affective disorder
  • social phobias

Not all serotonin deficiency symptoms are this obvious.

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

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

Low serotonin also impacts your overall health and even your longevity. (18)

Serotonin deficiency increases your risk for heart disease, dementia, and Alzheimer’s. (1920)

It can contribute to the severity of symptoms of asthma, fibromyalgia, migraines, and irritable bowel syndrome (IBS). (21222324)

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. (25)

They’re also more likely to exhibit carbohydrate cravings, binge eating, and subsequent weight gain. (26)

Overeating carbs is a way of self-medicating to raise serotonin levels. (27)

Men, on the other hand, are more prone to alcoholism, ADHD, and impulse control disorders. (2829)

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.

But more commonly it’s related to unhealthy lifestyle habits such as poor diet, excessive stress, artificial sweeteners, alcohol or caffeine, and a lack of sunlight. (30, 31)


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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 surprisingly, it’s not fully understood exactly how SSRIs work! (32)

Some users find them to be life-altering, but for many — up to 40% of those who try them — they don’t help. (33)

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

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 the real reason they work for some people. (34)

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

For many, dopamine deficiency is 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!

Most probably, the ultimate cause of depression will be found to be multifactorial and not the same for everyone.

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. (35)

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

Low Serotonin and Insomnia

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

Serotonin is a precursor to melatonin, the hormone responsible for managing your biological clock. (36)

Of course, there are many causes for insomnia that 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.


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See our MIND LAB PRO review.

Dr. Pat | Be Brain Fit

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 do contain serotonin — walnuts, hickory nuts, bananas, pineapple, kiwis, plums, and tomatoes — this is not an effective strategy since the serotonin in these foods does not enter the brain. (37)

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

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

But 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. (38)

There are only a handful of foods that increase serotonin naturally by other mechanisms — dark chocolate, cold-water fatty fish, green tea, fermented foods, and the spice turmeric. (39, 40, 41, 42, 43)

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

A blast of refined carbohydrates is a quick way to raise serotonin. (44)

But sugar also triggers a boost of stress-promoting cortisol that can last up to five hours. (45)

The most reliable way to raise your serotonin level with food is to 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 food. (46)

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

But tryptophan supplements provide a nice 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.

5-HTP has some potentially serious side effects.

It’s not intended for long-term use and should never be mixed with SSRIs or other antidepressant medications. (47)

Other supplements that increase serotonin safely include:

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

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

Expect to do some trial and error before you hit on the winning combination for you.

Increasing Serotonin with Lifestyle Choices

Some of the best ways to increase serotonin levels are not things you ingest but things you do.

Be Social

Simply spending time with friends can increase serotonin levels. (48)


Physical exercise can improve your mood by raising all of your feel-good brain chemicals, including serotonin. (4950)

Exercise has been found to work even better for depression if you do it outside. (51)

Compared with indoor exercise, exercising outdoors increases vitality, enthusiasm, pleasure, and self-esteem while lowering tension, depression, and fatigue. (52)

Even if you aren’t exercising, simply being in nature quiets the mind and enhances mental well-being. (53)

Get in the Sun

Sunlight boosts serotonin, plus you get the additional benefit of creating vitamin D, a known mood booster. (5455)

If sunlight isn’t available, selective exposure to bright artificial light can also help. (56)

But limit your artificial light exposure in the evening, especially the blue light from your electronic devices.

For instance, two hours of iPad use before bedtime can reduce your melatonin levels by 22%. (57)

Get Dirty

Dirt has been called the “new Prozac.”

Microbes found in soil increase serotonin levels. (58)

This may be a reason 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. (59)

It also changes your brainwave activity to make you feel more alert. (60)

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. (61)

Focus on happy memories.

Nip negative thinking and cognitive distortions in the bud. (62)

Positive self-talk and uplifting thoughts can promote serotonin synthesis while decreasing cortisol. (63)

Unfortunately, controlling the “random thought generator” in your head is not easy!


Meditation is the best technique for gaining control of your thoughts.

It also increases your resilience to stress while boosting serotonin. (64)

Feel more relaxed, focused & positive in a few minutes a day.

Overcoming Serotonin Deficiency: Take the Next Step

Depression, anxiety, and insomnia are classic symptoms of low serotonin, but there are many others as well.

Most antidepressant medications prescribed for these disorders are believed to work by increasing available serotonin in the brain.

But these drugs can have unwanted side effects and don’t work for everyone.

To raise your serotonin levels naturally, try this multi-pronged approach instead:

  • Include foods known to increase serotonin in your diet.
  • Strategically eat healthy carbohydrates.
  • Take serotonin-boosting supplements.
  • Get physical exercise and spend time outdoors.
  • Meditate and practice monitoring negative mental chatter.

The exact role serotonin plays in depression is controversial, but these lifestyle choices are not.

Incorporating them into your life can go a long way towards making you healthier and happier.