Serotonin Deficiency: Symptoms and Causes of Low Levels

The neurotransmitter responsible for regulating mood, social behavior, depression, and overall mental health.

Serotonin Deficiency: Symptoms and Causes of Low Levels

Serotonin is classified as one of the happy hormones, and low levels are most typically associated with depression and anxiety.

On the other hand, elevated levels can lead to a potentially dangerous condition known as serotonin syndrome.

To avoid issues of either kind requires maintaining optimal neurotransmitter levels for overall health and well-being.


    What is Serotonin Deficiency?

    In the adult brain, serotonin deficiency is a condition that indicates a neurotransmitter imbalance in the central nervous system.

    Low serotonin production is strongly associated with common conditions such as depression and anxiety, low energy, and various cognitive disorders, including dementia, schizophrenia, and other psychiatric conditions (1).

    There may be inferior serotonin function in the brain or a lack of serotonin receptors that receive serotonin, which engage in serotonin synthesis in these cases.

    It may even be that serotonin cannot reach receptors efficiently, or there may be a shortage of tryptophan, the amino acid from which serotonin is made.

    What Are The Symptoms of Low Serotonin?

    A low amount of serotonin in the brain can present many mental and physical health symptoms. Therefore, everything from behavior and mood problems to sleep and appetite is affected.

    People with low serotonin levels usually suffer in attention, perception, memory, anger, and motor skills.

    Psychological Symptoms

    Researchers believe that the psychological symptoms of low brain serotonin levels may happen when the production of new brain cells is suppressed.

    That is why antidepressants known as SSRIs are typically administered to boost serotonin levels.

    These medications can help kick off the production of new brain cells, which allows negative thoughts and depression to lift.

    Common psychological conditions associated with low brain serotonin include major depressive disorder, obsessive-compulsive disorder, and generalized anxiety disorder, among many others.

    Physical Symptoms

    The physical symptoms of serotonin deficiency can include disrupted sleeping patterns, slow metabolism, an imbalance in energy levels, irregular digestion, blood sugar imbalances, and reduced interest in sex.

    Other indicators of low serotonin are typically associated with physical conditions like fatigue, osteoporosis, diabetes, obesity, cardiovascular disease, and digestive distress such as IBS.

    What Causes Low Serotonin Levels?

    Various factors can affect serotonin levels. For example, low brain levels of serotonin may happen due to changes brought on by age, poor dietary choices, chronic stress, a sedentary lifestyle, or even a lack of exposure to natural light.

    Some people may have a singular cause, whereas others may be affected by more than one factor.

    Research shows that serotonin nerve cells and nerve signal loss are normal with aging. As a result of these changes, mental health issues such as Alzheimer’s disease and others can bring about behavioral changes in the elderly (2).

    Additional research also shows that a deficit in serotonergic neurotransmission is integral to developing major depression in later life.

    Chronic Stress

    Chronic stress can affect neurotransmitters in the brain, including cortisol and serotonin, which modulate mood and cognition.

    For example, research shows that higher and prolonged cortisol levels in the brain have been associated with shrinking the size of the hippocampus.

    The reduced hippocampus, constantly exposed to stress and inflammation, is most often observed in depressed individuals than in healthy people (3).

    Also, people who suffer from chronic stress and low serotonin levels are more likely to experience a sleep disorder of some sort and disturbances with circadian rhythm.

    Medication and Drug Abuse

    Certain prescription medications and drugs can interact with naturally occurring chemicals in the brain, including serotonin.

    The National Institute on Drug Abuse explains that dopamine and serotonin are the two neurotransmitters most commonly affected by drug abuse.

    Drugs that manipulate dopamine levels affect an individual’s motor functioning, motivation, positive mood, and sense of pleasure.

    In contrast, those that affect serotonin influence how someone feels emotions learns, remembers, and sleeps.

    Hormonal Changes

    Hormone imbalances may also cause low serotonin. While some hormones may boost serotonin, others can deplete serotonin levels.

    Estrogen, for instance, increases serotonin along with the number of serotonin receptors in the brain. However, low estrogen levels may also lower the production of serotonin (4).

    Another hormone that tends to lower serotonin is cortisol. Excess secretion and circulation of cortisol affect serotonin levels and those of other transmitters.

    Among these, elevated cortisol depletes dopamine, which lowers activity in the brain’s pleasure pathways, reduces norepinephrine, which leads to a lack of motivation and alertness, and diminishes serotonin, which reduces feelings of happiness and well-being (5).

    Nutritional Deficiencies

    Serotonin plays an essential part in digestion and gut health. Because outside other than the brain, most of it is found in the GI tract, where it helps promote healthy digestion. Also, given the gut-brain axis, it can help resolve various digestive issues.

    One of the causes of low serotonin is not having enough tryptophan in the body. Since this amino acid can only be obtained from food, any deficiency will make less serotonin (6).

    People who suffer from a poor diet need to make dietary changes and include foods that can help produce more tryptophan. Likewise, vitamin B6 and vitamin D deficiency have also been linked to lower levels of serotonin.

    Lack of Sunlight

    Sunlight and darkness both initiate the dispensation of certain substances in the brain. Sunlight, for instance, triggers serotonin, while darkness triggers melatonin.

    Serotonin helps improve attitude, focus, and calm. Its effects are triggered when sunlight enters the body through the eyes. Sunlight activates specific areas in the retina that dispense serotonin (7).

    When someone doesn’t get adequate sunlight, their serotonin drops naturally, presenting an increased risk of depression and anxiety.

    How is Serotonin Deficiency Diagnosed?

    Doctors may conduct a serotonin blood test to measure serotonin in the blood. For the most part, however, blood tests are mainly done to check for serotonin-producing tumors.

    Typically, doctors don’t diagnose a serotonin deficiency but treat symptoms instead. Mainly because detecting a serotonin deficiency can be hard to pin down, and it remains unclear whether the symptoms cause the deficiency or vice versa.

    While serotonin blood levels don’t accurately reflect the amount in the brain, symptoms of serotonin deficiency can give medical professionals a fair idea of whether there is a deficit or not.

    Likewise, urine tests are also unreliable as they can only ascertain how much serotonin the body produces but don’t measure the amount in the brain.

    How To Treat Serotonin Deficiency?

    There are many ways to raise serotonin levels naturally or with some help from certain types of medication and nootropics.

    The most common treatment options for increasing serotonin include the following ways:

    Selective Serotonin Reuptake Inhibitors (SSRIs)

    SSRI antidepressants are typically prescribed to people with anxiety and OCD to boost serotonin.

    SSRIs work by helping the brain maintain normal levels of the neurotransmitter serotonin to regulate energy, appetite, thinking, sex drive, and much more (8).

    They do so by blocking the reuptake of serotonin from neurons that release it. SSRIs for anxiety include Zoloft, Prozac, Lexapro, Celexa., Luvox, Paxil, and Pexeva.

    While SSRIs can cause side effects, most people do not have any serious ones. Often side effects may only last for the first one to two weeks as the body adjusts to the new medications.

    Typical side effects can include nausea, diarrhea, dizziness, dry mouth, drowsiness, sexual dysfunction such as erectile dysfunction or low libido. Conversely, some people may experience insomnia or improved sleep and weight gain.

    Serotonin Norepinephrine Reuptake Inhibitors (SNRIs)

    Another class of antidepressant medications known as serotonin-norepinephrine reuptake inhibitors, SNRIs, are used for treating depression and or anxiety. Some doctors may also prescribe these to manage chronic pain conditions.

    These antidepressants work by helping the brain maintain serotonin and norepinephrine within the normal range. Examples of SNRIs for anxiety include Cymbalta and Effexor XR.

    These can also share similar side effects with SSRIs, such as constipation, dizziness, drowsiness, fatigue, headaches, weight gain, loss of appetite, nausea, sexual problems, sleep problems, profuse sweating, and an upset stomach.


    Low serotonin may also be corrected by using dietary supplements and nootropics. Some common recommendations that can help produce serotonin include supplements that contain pure tryptophan, SAM-e, 5-HTP, Saint John’s wort, and probiotics.

    Natural supplements make for an effective non-drug option that can help produce serotonin.

    Different supplements follow different mechanisms where some may yield amino acids that are precursors of serotonin while others may be essential cofactors for serotonin synthesis.

    Many nootropic supplements have antidepressant properties, whereas others collaborate synergistically with other serotonin-boosting substances.

    It is crucial to consult your doctor before trying any serotonin-enhancing supplements for self-medical treatment.


    Consumption of certain foods can help produce more serotonin. While eating these foods won’t directly increase serotonin, many will contain the essential amino acid tryptophan, which will help the body produce more serotonin.

    Options like salmon, chicken, goose, turkey, eggs, spinach, seeds, milk, soy products, and nuts can help improve serotonin levels.

    It is also vital to include carbs in the diet as tryptophan needs carbohydrates to reach the brain and create serotonin. As such, tryptophan-rich foods are most effective when consumed alongside carbohydrates (9).


    Studies suggest that regular exercise can be as effective a treatment for low mood or depression as psychotherapy or antidepressant medication.

    A 30-minute ritual of daily exercise, including aerobics, can significantly increase serotonin levels in the body. The best recommendations for doing so include walking, biking, running, and swimming.

    Even other forms of exercise such as Pilates, yoga, and Tai chi can also increase serotonin, just not to the same extent as aerobics (10).

    Mood Induction

    This technique involves thinking about things that make you happy or feel good. Thinking about pleasant thoughts can help increase serotonin in the brain, reflecting an improved mood in general.

    You can do so by either visualizing a positive experience from the past, listening to music, or even going through photos of things that make you happy. This could be anything from a favorite place, close friends, or even your pet.

    Mood induction is a natural way to increase serotonin without any outside intervention. However, serotonin does not always work in isolation and often uses other neurotransmitters to help improve mood (11).

    Bright Light

    Because low serotonin generally prevails in the winter or when there isn’t adequate exposure to sunlight, light therapy is often recommended to restore levels.

    Not getting enough hours of sunlight exposure can also result in circadian disruption, difficulty sleeping, and low mood.

    Based on the evidence, experts recommend spending some time in the sun or increasing serotonin with bright light exposure from a light therapy box to increase serotonin.


    Serotonin deficiency causes many symptoms like sleep changes, memory or learning issues, eating disorders, and depression.

    If you suspect symptoms of a serotonin deficiency, the recommended course of action is to work with your health care provider and narrow down potential causes before developing a treatment plan.

    Your doctor or therapist can best recommend whether you need prescription drugs or can benefit from natural supplements to treat your condition.

    They can also determine whether exercise, diet, or light therapy may be beneficial additions to your treatment regimen.