What is Serotonin? Functions and Effects In The Brain

The happy hormone that influences your health and well-being.

What is Serotonin? Functions and Effects In The Brain

Every time you feel a burst of joy, excitement, or satisfaction, you can acknowledge serotonin for it.

Serotonin is best known for regulating mood and feelings of happiness, and because of that, it has the nickname “the happy chemical.”

Most people recognize this hormone because the deficiency is associated with depression and anxiety.

But serotonin is much more than that. It is one of the most extensively researched neurotransmitters exhibiting a range of functions both in the brain and the body.


    What is Serotonin?

    Serotonin is the essential hormone responsible for stabilizing mood, feelings of well-being, and happiness.

    It plays an essential role in communication and sends signals between the central nervous system’s brain and other nerve cells, enabling a person to sleep, eat, and digest well.

    Of the approximately 14 million brain cells in our head, it’s estimated that serotonin impacts just about every one of them, either directly or indirectly.

    However, if the human brain has too little serotonin, it may lead to different physical and mental problems such as depression and anxiety. On the other hand, too much serotonin in the brain can trigger excessive nerve cell activity.

    Serotonin Production

    It is estimated that 90% of serotonin is found in the digestive system. The rest is present in the central nervous system, including the human brain.

    The body undergoes a conversion biochemically with its precursor tryptophan to produce serotonin.

    Tryptophan is an amino acid and building block for proteins needed to make serotonin. Cells that produce serotonin wield tryptophan alongside tryptophan hydroxylase to form serotonin.

    That is why consuming tryptophan supplements and eating foods rich in tryptophan are excellent ways to increase this happy chemical naturally.

    Serotonin Release

    Serotonin is unique because two different genes at two various places host serotonin biosynthesis.

    It is released in the brain, where it helps with mood and memory, and also it is released in the gut to promote healthy digestion.

    After that, serotonin release helps to improve sleep, sexual function, bone health, and blood clotting.

    Serotonin Receptors

    Serotonin receptors are mainly found in the central and peripheral nervous systems.

    Additionally, receptors are also found in the muscle lining of the gut, where they enhance food movement of what you eat through interstates.

    What Are The Serotonin Functions and Benefits?

    Serotonin plays multifaceted roles by carrying signals between different parts of the brain.

    For instance, it plays a part in consciousness, cognition, emotion, attention, and it can also modulate a host of other bodily systems.

    While it’s usually classified as a neurotransmitter, it also works as a hormone that gets released into the bloodstream to send messages to different body parts, including blood platelets and the gut.


    Serotonin affects happiness and helps to regulate your mood. For example, low levels of serotonin are linked to depression, while increased levels may decrease arousal.

    As it works in the capacity of a natural mood stabilizer, serotonin can uplift mood naturally and is frequently used to treat various mood disorders.

    Research suggests that when there is more serotonin in the brain, people experience improvements in mood (1).

    When someone has a faulty serotonin receptor or low tryptophan, they may suffer from depression, agitation, panic attacks, anxiety, anger management issues, and other mood disorders.

    Given that much of the serotonin the body produces is in the gut, you can support your mental well-being by fortifying gut bacteria and the diet.

    Mental Health

    Serotonin is essential for mental health as high levels in the brain boost cognitive abilities, including memory and learning speed.

    On the flip side, an imbalance in levels has also been associated with mental health issues such as anxiety, depression, and obsessive-compulsive disorder.

    Helping the body produce or maintain enough serotonin can alleviate depressive symptoms and help to treat the mental illness.

    The notion that serotonin correlates to depression is also supported by evidence that individuals who experience a comedown after alcohol consumption or drug use report feeling dismal and depressed.

    Again, the reason is that recreational drugs and alcohol cause levels of serotonin to surge before dipping rather quickly. The sudden decline in levels impacts mood negatively during the comedown stage.

    While many people use psychotropic medications to boost serotonin levels to regulate anxiety and treat depression, drugs carry a significant risk of imbalances and having serotonin levels too high in the system.


    Serotonin in the brain helps to regulate parts that controls sleep and waking. It may help manage sleep cycles as the body utilizes it to synthesize melatonin.

    Melatonin is created at night and performs a fundamental role in regulating the body’s biological clock and governs the entire sleep-wake cycle.

    While the two perform opposite functions, they need to work in harmony to balance the circadian rhythm.

    Melatonin levels are boosted when it’s dark, and on the other hand, serotonin levels increase in shine and light environments.

    So whereas the former helps you get to sleep, the latter enables you to feel awake when you get up the next day.


    Serotonin is also found in the digestive tract, which can help control your bowel movements and healthy function. However, low levels of serotonin in the gut have been linked to irritable bowel syndrome, IBS.

    When there isn’t enough serotonin in the stomach and intestines, the person may experience irregular bowel movements, diarrhea, constipation, bloating, and abdominal cramping.

    Specific serotonin receptors are vital mediators of motility, secretion, and even painful sensation in the digestive system. Unfortunately, people with IBS have significantly lower serotonin transporters in the cells lining the bowel.

    This means that patients with IBS have an inadequate mechanism that causes serotonin to stay longer, triggering troublesome bowel changes.

    Animal studies show that specific gut microbiota may affect serotonin production in the gut. Findings from the study show that a group of indigenous bacteria may increase and balance serotonin levels that can help increase gastrointestinal motility (2).

    At the same time, the relationship connecting the brain and gastrointestinal disorder suggest that adequate serotonin may treat related brain-gut conditions simultaneously.


    An excess of serotonin may cause you to become nauseous. This is because it pushes out unhealthy or upsetting food more quickly in diarrhea.

    That is why while taking SSRIs, people often report nausea as the number one side effect. Since these medications boost serotonin levels to treat severe depression and anxiety, nausea can occur.

    An increase in levels stimulates receptors in the GI tract and the brain. The combined stimulatory effect on both can trigger digestive symptoms such as vomiting, diarrhea, and a loss of appetite.

    For some patients, nausea may become so overwhelming that they may have to stop treatment. For others, stopping taking antidepressants can also cause nausea and vomiting.

    Recognized as antidepressant discontinuation syndrome or antidepressant withdrawal, individuals may experience gastrointestinal symptoms. Unfortunately, withdrawal symptoms can sometimes persist for several weeks and even lead to rebound depression.

    Blood Clotting

    Serotonin can have different effects on cardiovascular health. For example, it may increase or decrease blood pressure, and in isolated blood vessels, it can cause contraction or relaxation.

    In case excess serotonin levels do not get used up in the gut, they go back into the bloodstream, where blood platelets quickly take it up.

    These tiny blood cells store up serotonin and release some of it to heal wounds, cuts, bruises, and other kinds of tissue damage.

    When a person has higher serotonin levels, the tiny arteries in the circulatory system known as arterioles become narrow. As these small arteries reduce in size, blood flow slows down. This process is key to the function of blood clotting, which is also a vital step in healing wounds.

    Bone Health

    Bone health is also affected by serotonin levels. However, the site of its production has different effects on bone mass.

    When production happens peripherally, serotonin works in a hormonal capacity and inhibits bone formation.

    On the other hand, when it is produced in the brain, it becomes a neurotransmitter that exerts a dominant and positive effect on bone formation and limits bone resorption.

    Research shows that very high levels of this hormone in the bones can lead to osteoporosis, making bones weaker. As a result, inhibiting serotonin in the gut could potentially cure bone-related conditions.

    Research also shows that SSRIs are linked to decreased bone mineral density and could make a person more susceptible to fractures (3).

    Sexual Function

    Serotonin plays a part in affecting the intensity of your sexual urges and how often you feel them. Altering the body’s serotonin levels may cause hypoactive sexual desire or low libido.

    Serotonin is recycled but into brain cells after release by serotonin transporters to be broken down and used again.

    But when medications like SSRIs block these transporters, serotonin remains in the synapses between built-up nerve cells, resulting in higher serotonin signaling in the brain.

    This affects sexual behavior. Generally speaking, high levels of serotonin inhibit sexual behavior and decrease arousal. Consequently, antidepressants that increase serotonin can cause problems like a long time to ejaculate in men.

    The potential sexual side effects of taking SSRIs for some women can improve with time as the body adjusts to higher serotonin levels.

    However, if sexual symptoms don’t improve, doctors may consider decreasing your dosage as long as your mood is stable.

    One study found that 70% of people with SSRI-related sexual problems reported relief when their dose is cut in half.

    What Affects Serotonin Levels?

    Several different factors can affect serotonin production. Brain serotonin increases or falls based on the following factors:

    • Prescription medications such as selective serotonin reuptake inhibitors (SSRIs), illicit drugs, or supplements.
    • Sometimes inherited genetic disorders may also affect the body’s ability to metabolize serotonin.
    • Lifestyle and other aspects play a role, such as hormonal shifts, menopause, pregnancy, and advancing age.
    • Other things that may affect serotonin levels include a lack of sunlight, nutrition, and chronic stress.

    What Are The Risks of Serotonin Deficiency?

    Low levels of serotonin are often associated with many behavioral and emotional disorders. Therefore, research studies confirm that low serotonin levels can lead to depression, anxiety, suicidal behavior, and obsessive-compulsive disorder.

    Since serotonin helps regulate the body’s internal clock, a serotonin deficiency may impact the ability to feel sleepy, remain asleep, have insomnia, and wake up refreshed in the morning.

    Its role in how muscles behave means that low serotonin can cause chronic pain. In addition, low levels are strongly correlated with fibromyalgia, and people with the condition may get relief from antidepressants that raise serotonin levels.

    Likewise, some studies have linked serotonin to the proper functioning of memory and learning, so any difficulties in these areas could indicate a serotonin issue.

    Anxiety disorders, including obsessive-compulsive forms, that occur suddenly and appears unrelated to any trigger may indicate an issue with low serotonin levels.

    Research has shown that people with low serotonin have appetite issues or eating disorders, given the apparent correlation between the hormone and the digestive tract. This may include not eating enough, overeating, or alternating between the two.

    One of the ways to increase serotonin levels naturally is possible by changing the diet, including foods containing dietary tryptophan.

    Protein-rich foods such as eggs, turkey, salmon, and cheese are good sources of tryptophan that can provide the body with the raw substance it needs to make enough serotonin.

    Another way to go is to take nootropic supplements to increase serotonin levels. These may typically include products that contain vitamin B6, 5-HTP, pure tryptophan, and probiotics.

    Even engaging in regular exercise can help. In particular, aerobic exercise such as running, swimming, or aerobics can be particularly effective.

    What Happens If You Have Too Much Serotonin?

    A disease identified as serotonin syndrome can occur when you take certain medications that increase levels leading to side effects. Also known as serotonin toxicity, the condition can present severe symptoms that result from higher levels in the body.

    In serotonin syndrome, too much chemical production can cause mild symptoms such as shivering, heavy sweating, restlessness, confusion, headaches, twitching muscles, and digestive complaints.

    More severe serotonin syndrome symptoms can include high fever, seizures, unconsciousness, or irregular or rapid heartbeat. While the syndrome can happen to anyone, some people may be at an increased risk.

    For example, anyone taking medication that can raise serotonin levels is more susceptible. Also, the risk of serotonin toxicity may increase if you take herbal supplements or illicit drugs known to enhance its levels.

    Typically, antidepressant medication is linked to serotonin syndrome.

    While most people can safely take serotonergic antidepressants under the guidance of their physicians, anyone whose body process the hormone differently or can’t process a large amount of it should only use specific medication under professional medical advice.

    Many types of antidepressants, including selective serotonin reuptake inhibitors (SSRIs) such as Prozac, Celexa, or Zoloft, can trigger symptoms of serotonin syndrome.

    According to a recent study, increased use of antidepressants may also be associated with developing the risk of fatal blood clots (4). Also, other drugs like SSRIs and norepinephrine reuptake inhibitors (NRIs) can produce similar effects.

    The most prevalent symptoms of serotonin syndrome include mood changes, confusion, digestive distress, including diarrhea, dilated pupils, arrhythmia, fever, muscle stiffness in the legs, shivering or sweating, an increased heart rate, or high blood pressure.

    While it is not very common, serotonin syndrome may become a potentially life-threatening condition in some cases.

    It is possible to regulate high levels of serotonin and achieve optimal levels by modulating serotonin synthesis with the right supplements, changing your dietary habits, and getting regular exercise.


    Serotonin is one of the essential feel-good neurotransmitters. While low levels are linked to depression, too much is linked to a long list of side effects that may be dangerous if left untreated.

    Antidepressants usually work by increasing levels, but they come with a huge risk of raising too much serotonin levels. Because of that, many natural nootropics and dietary supplements may be a better solution.

    The most vital thing to remember is to keep your levels within the normal range and eventually consult your doctor if there are any significant imbalances.