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What Is Serotonin?

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You may have heard that serotonin is what makes you feel happy, but it does a lot more than that. In fact, serotonin seems to affect virtually every human behavior, from eating and sleeping to mood control and sexuality. It's actually hard to find a human behavior that isn't affected by serotonin in some way—although researchers are still studying exactly how it works in all these diverse contexts.[1] Read on to find out more about what scientists know about serotonin. You'll learn how it affects your body and your mood, as well as how you can boost your own serotonin levels.

What is serotonin?

Serotonin is a neurotransmitter in your brain. In your nervous system, neurotransmitters are created by neurons and used to send messages to other neurons, or "receptors." Once the message is sent, the neurotransmitter that sent the message is reabsorbed by your body—its job is done.[2]

  • Serotonin is created in your brain stem and sent through your central nervous system throughout your body.

Serotonin acts as a hormone in your gut. Cells produce and release serotonin throughout your gastrointestinal tract. As a hormone, it also sends messages to other cells, but isn't reabsorbed as quickly as a neurotransmitter.[3]

  • As a hormone, serotonin helps stimulate the muscles in your gut so food can be digested properly. It can also help protect you from gastrointestinal diseases, such as irritable bowel syndrome (IBS).[4]

What does serotonin do?

Aids in blood clotting. If you have a cut or other wound, serotonin in your blood constricts your blood vessels to slow bleeding and allow the blood to clot.[5] This was the first function of serotonin scientists discovered—all the way back in 1948.[6]

  • If you inject serotonin directly into the blood, it's painful and irritating. The hormone is found in wasp and scorpion venom and is responsible for the painful prickling and tingling sensation you feel at the site of the sting.

Regulates sleep cycle. Neurons shoot out short bursts of serotonin during quiet waking moments. Those bursts slow as you get ready for sleep and while you're sleeping. When that system is disrupted, so is sleep. So it seems that serotonin keeps your circadian rhythm functioning properly, but that's really all researchers know. [7]

  • Your body also uses serotonin to make melatonin, which influences the timing of your circadian rhythm, including when you start to feel tired and how long it takes you to go to sleep.

Influences appetite. Scientists know that activating serotonin receptors decreases the amount of food you eat while blocking the transmission of serotonin increases it—but they don't know exactly how or why this happens. It's thought that serotonin affects how much you eat before you feel full, and how long that feeling of fullness lasts before you're hungry again.[8]

  • Researchers speculate that low serotonin might be a partial cause of obesity, but this is still being studied.
  • Serotonin also affects digestion. Low levels of serotonin are associated with gut disorders, including Irritable Bowel Syndrome (IBS).[9]

Inhibits sexual activity and libido. High levels of serotonin tend to indicate a low libido, while low levels of serotonin correspond with a high libido—but that's not the whole story. Technically, whether serotonin inhibits or stimulates your libido depends on which receptors in the brain are activated.[10]

  • Sexual dysfunction is a common side effect of antidepressants that target serotonin. This side effect is less common with drugs that also increase dopamine activity, which leads researchers to believe that serotonin and dopamine work together to influence healthy sexual functioning.

Influences learning, memory, and executive function. The regions of your brain responsible for learning and memory contain a lot of serotonin receptors. Neurons release serotonin when you're learning or when you need to remember something, but researchers don't know exactly what effect serotonin itself has on the process.[11]

  • People diagnosed with ADHD, autism, and some mood disorders often have difficulty with learning, memory, and executive function. Typically, they also have low levels of serotonin. Increasing serotonin sometimes helps, but researchers still don't understand exactly how.

Regulates bone density. Research has shown that a high level of circulating serotonin—the hormone version of serotonin produced in the gut—is associated with reduced bone density. In contrast, serotonin in the brain helps the body build new bone tissue and maintain existing bones.[12]

  • Research is ongoing on the role of serotonin in bone density. Studies have also shown that people who take drugs that increase serotonin are at higher risk for bone loss.[13]

Serotonin and Mental Health

Mood control. Scientists have determined that specific serotonin receptors in your brain might be responsible for specific moods. Specific receptors are also tied to specific behaviors, so your serotonin levels may dictate how you respond to things that happen to you. However, researchers aren't clear on exactly how serotonin works to control and regulate mood—they only know that it does.[14]

  • For example, researchers know serotonin affects your ability to control your mood and react appropriately to various situations. But at the same time, research has shown that depleting serotonin levels in otherwise healthy individuals has no effect on their mood control. So serotonin's role remains something of a mystery.
  • Drugs targeting serotonin and serotonin receptors in some way are either in use or being tested for use to treat virtually every mental disorder.[15]

Depression and irritability. Low serotonin in the brain can lead you to be frustrated more quickly than you used to be. A lack of serotonin also depletes your energy so you're quickly wiped out. When you do things that used to give you pleasure, you might find they don't give you a boost like they did in the past.[16]

  • Behaviors arising from these moods can also greatly affect your everyday life. For example, if you lash out at someone in hostility, you might not get the service or attention you need.
  • Drugs that treat anxiety and mood disorders often aim at increasing the available serotonin. For many people, this seems to work—but researchers aren't really sure exactly how or why.[17]

Mental decline. Serotonin plays a role in learning and memory. Studies show that not having enough serotonin can cause you to have problems with memory and with processing the things that are going on around you. Researchers believe low serotonin might be the cause of this decline, rather than just another symptom of it.[18]

  • Patients with Alzheimer's disease and dementia tend to have extremely low levels of serotonin in their brains. Researchers believe that increasing serotonin early on could slow the progression of these diseases.

What medications target serotonin?

SSRIs block serotonin from being reabsorbed by the nerve cells. Selective serotonin reuptake inhibitors make sure the serotonin you have is available in your brain for longer. Even though this class of drugs doesn't directly increase the amount of serotonin you have, the effect is similar.[19]

  • Common SSRIs include fluoxetine (Prozac), paroxetine (Paxil, Seroxat), and sertraline (Zoloft, Lustral).
  • This class of drug is the most widely prescribed antidepressant. Doctors also prescribe SSRIs to treat anxiety, post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), and other conditions that involve low levels of serotonin.

SNRIs target serotonin and norepinephrine to increase the effectiveness of serotonin. This class of serotonin and norepinephrine reuptake inhibitors blocks or delays the reabsorption of both serotonin and norepinephrine. Norepinephrine works along with serotonin and dopamine to regulate emotions and thought processes.[20]

  • Common SNRIs are venlafaxine (Effexor), desvenlafaxine (Pristiq), and duloxetine (Cymbalta).
  • SNRIs are prescribed to treat symptoms of low mood, irritability, restlessness, and anxiety in conditions such as major depressive disorder (MDD), bipolar depression, Fibromyalgia, panic and anxiety disorders, and social phobias.

Taking Medication to Increase Serotonin

Discuss your symptoms with your doctor. Talk to your doctor about what you've been feeling or thinking, and how long you've had these thoughts and feelings. Let them know about what you've done (if anything) to try to make yourself feel better and what happened as a result.[21]

  • Remind your doctor of any other medications or supplements you're taking, as well as any allergies you might have.
  • Your doctor might also recommend that you see a therapist as well. Antidepressants tend to work better when they are combined with talk therapy.

Take your medication as prescribed for at least a month. It can take 4-6 weeks before you'll start to notice any difference in your thinking, mood, or behavior after you start taking an SSRI. Talk therapy can help a lot if you're feeling frustrated while waiting for the drug to take effect.[22]

  • If it's been 6-8 weeks and you notice no change at all, your doctor might decide to switch you to a different SSRI.
  • Some people go through several different drugs before they find the one that's right for them. The SSRI treatment process involves a lot of experimentation to find the best drug at the right dose. Try not to get discouraged if you find yourself in this situation—each medication you try gets you closer to one that works for you.

Call your doctor immediately if your depression or anxiety gets worse. Serotonin neurons actually transmit both serotonin and glutamate. While serotonin has been linked to motivation, it's the glutamate component that's associated with pleasure. When you first start taking SSRIs, the glutamate component is suppressed while serotonin is enhanced—which can cause you to feel more agitated or restless. Glutamate levels tend to stabilize after a couple of weeks.[23]

  • You might also start to feel symptoms of mania, where you have a lot of energy and act out on impulses. This usually means your dosage is too high, and things will likely improve for you on a lower dose.[24]
  • Whatever you do, don't immediately stop taking your medication, even if the side effects frighten you. Stopping an antidepressant without tapering off can cause withdrawal symptoms. Call your doctor and they'll know what to do.

Monitor your moods and thoughts as you take the prescribed dose. Keep your doctor or therapist in the loop about your condition and progress. You won't necessarily have to take antidepressants forever, but it does take time for your body and brain chemistry to change. Try to be patient and trust the timeline provided by your doctor. However, if you feel like that really isn't working for you, don't be afraid to get a second opinion.[25]

  • Expect that you'll probably take the drug for at least a year if not longer. Your doctor might have a general idea of how long they think you'll need to take it, but they also might not. It varies from person to person.

Taper off the medication gradually if you want to stop taking it. While you can't necessarily get addicted to SSRIs, you can experience withdrawal symptoms if you just suddenly stop taking them. These symptoms include headaches, insomnia, anxiety, and frequent mood changes. Talk to your doctor first, and they'll prescribe a slightly lower dose so you can begin tapering off.[26]

  • While you're tapering off, monitor your mood and your thoughts and feelings closely. If you feel like things are starting to get worse or you're starting to lose control, tell your doctor immediately. They may suggest increasing your dose.

Increasing Serotonin Naturally

Exercise for at least 20 minutes every day to increase serotonin. Experts have theorized that physical activity triggers a release of serotonin. This might explain why people with active lifestyles have less anxiety and depression than people with sedentary lifestyles. Regular exercise might even treat depression and anxiety as well as SSRIs can![27]

  • Exercise tends to give you even more of a boost if you do something you actually enjoy doing and can look forward to. For example, if you enjoy soccer, you might join a local community soccer team or schedule a regular pick-up game with friends.

Spend time in direct sunlight to increase serotonin production. Light therapy has long been a treatment for seasonal affective disorder, but it might help with depression and anxiety as well. Research shows that serotonin production and activity increase significantly when you're exposed to bright light.[28]

  • If you live in a place where sunlight is scarce, particularly in the winter months, you might want to invest in a daylight lamp. You can buy these online and at many home improvement stores. Sitting under the lamp for just a few hours a day could significantly increase your serotonin.

Meditate for 20 minutes a day to boost serotonin in your brain. When your brain is in a meditative state, it releases serotonin. This mental state provides additional benefits to your brain as well, lowering anxiety levels and making it easier for you to focus and concentrate.[29]

  • If 20 minutes of meditation seems intimidating, break it up. Doing a simple breathing exercise for a couple of minutes every hour will likely have the same effect.

Add more complex carbs to your diet. Your body creates serotonin from tryptophan, so eating foods that are high in tryptophan can increase your serotonin production. Vegetables, fruits, legumes, and whole grains are good ways to get tryptophan into your brain.[30]

  • You might think foods like turkey are high in tryptophan, and they are—unfortunately, the high protein keeps a lot of the tryptophan from getting to your brain. Your body also doesn't convert the tryptophan from turkey into serotonin very efficiently.

What is serotonin syndrome?

Serotonin syndrome is a condition where you have too much serotonin. Your brain never makes too much serotonin on its own, so this condition doesn't occur naturally. It only happens if you overdose on medications or supplements that increase your serotonin.[31]

  • Symptoms of serotonin syndrome range from mild (diarrhea, sweating or shivering, fever) to severe (increased heart rate and blood pressure). It can be deadly. If you believe you might have serotonin syndrome, seek medical treatment immediately.
  • Drugs and supplements that affect serotonin include opioids, over-the-counter (OTC) cough and cold medications, migraine medications, anti-nausea drugs, and herbal supplements such as St. John's wort.
  • Always tell your doctors about any drugs or supplements you're taking. Only take prescription medications that are prescribed to you at the dose prescribed.