- What is Serotonin?
- Physical health
- Low Serotonin
- Increasing Serotonin Levels
- Selective Serotonin Re-uptake Inhibitors (SSRIs)
- Tricyclic antidepressants (TCAs)
- Monoamine oxidase inhibitors (MAOIs)
- Too Much Serotonin
- How to reference this article:
- APA Style References
- What Is Serotonin Syndrome? A Potential Danger of SSRIs
- What are the symptoms of serotonin syndrome?
- Herbal supplements
- Antibiotics, antifungals, and antivirals
- Pain medications
- Anti-nausea medications
- Migraine medications
- Serotonin Syndrome: Symptoms, Causes, Treatments
- What is serotonin syndrome?
- What are the most common serotonin syndrome symptoms?
- Serotonin: What to Know
- A Happy Chemical: Serotonin and Mood
- The Role of Serotonin in Brain Function
- Gut Bacteria and Serotonin Production
- Selective Serotonin Reuptake Inhibitors (SSRIs)
- How Do SSRI Drugs Work?
- Who Benefits From Use of SSRIs?
- Serotonin Foods and Supplements
- Serotonin Syndrome
What is Serotonin?
- Serotonin is a neurotransmitter (chemical messenger) produced within the central nervoussystem (CNS) that contributes to feelings of happiness.
- Too little serotonin has shown associations with depressed feelings, sadness, and fatigue. Too much serotonin, however, could result in serotonin syndrome, which could lead to symptoms of restlessness, hallucinations, and confusion.
- Serotonin is also known as a hormone within the enteric nervous system of the body, primarily found within the gastrointestinal tract (gut).
- In the enteric nervous system, serotonin plays a role in numerous biological processes such as controlling cardiovascular function, bladder control, and bowel movements.
- Serotonin in the brain, however, is of interest to psychologists as its role as a neurotransmitter is thought to contribute to many important functions such as playing a role in mood, especially in relation to mood disorders such as depression and anxiety.
The scientific name for serotonin is 5-hydroxytryptamine (5-HT) and is a neurotransmitter of the monoamine group that contain amino acids. The monoamine group of neurotransmitters play a role in many functions such as decision-making, emotions, happiness, rewards, and have associations with mental health conditions as a result.
Within the brain, serotonin mostly originates in the brain stem within a cluster of nuclei called the Raphe nuclei.
Serotonergic fibers are then synthesized from the Raphe nuclei and projected to the nucleus accumbens, part of the basal forebrain that is known as the circuit area for rewards.
Here it is then projected throughout the brain, including the lobes of the brain, hippocampus, cerebellum, and spinal cord.
During neurotransmission, serotonin is released into the synaptic cleft from the terminals of the presynaptic neuron.
When it reaches this gap, the serotonin will either be taken up by serotonin receptors on the postsynaptic neuron and continues down the next neuron via electrical impulses, or the serotonin may get degraded by an enzyme called monoamine oxidase, or it will be taken back up into the presynaptic neuron by the serotonin transporter (SERT).
There are 15 types of serotonin receptors with 6 families that are G-protein coupled receptors which work by mediating cellular responses (5-HT1, 5-HT2, 5-HT4, 5-HT5, 5-HT6, 5-HT7) and 1 family that consists of ligand-gated ion channels (5-HT3) which works to depolarise the plasma membranes.Serotonin is under the classification of an inhibitory neurotransmitter as it has inhibitory effects on the neurons, decreasing the lihood that the neurons will fire action potential.
This contrasts with excitatory neurotransmitters which have excitatory effects on the neurons. Serotonin does not therefore stimulate the brain; it instead balances out the excessive excitatory effects of other neurotransmitters.
Since serotonin is projected from the brain stem and reaches most regions of the brain, it has a wide array of effects on many aspects of behavior.
The neuropsychological processes modulated by serotonin can include having a role in attention, perception, reward, anger, aggression, memory, motor skills, and appetite. In fact, it is difficult to identify a human behavior that is not regulated by serotonin in some way.
One of the key interests in serotonin, and its most well-known function is its effect on modulating mood. Serotonin is considered to be a natural mood stabiliser and when functioning normally, it is believed to help people with feeling happy, calm, focused, and emotionally stable.
Serotonin is also thought to regulate anxiety and reduce depressed feelings. It is important to note that serotonin does not work in isolation, and it often uses other neurotransmitters such as dopamine to help alleviate mood.
Elsewhere in the body, serotonin helps with sleep. There are specific regions in the brain that control when we fall asleep, regulate sleep patterns, and controls when we wake up.
The parts of the brain that are responsible for regulating sleep also have serotonin receptors. Serotonin is responsible for stimulating the parts of the brain that control sleep and wakefulness.
Whether someone is sleeping or is awake is dependant on which serotonin receptor is used. Melatonin, which is a hormone vital to the functioning of sleep, requires serotonin so that melatonin can be produced.
Outside of the brain, serotonin also has important roles in other parts of the body, with most of the serotonin being found in the gastrointestinal tract rather than the brain.
Serotonin is required in the gut to promote healthy digestion. Similarly, serotonin helps with maintaining bone health, eating, sexual function, and healing wounds by blood clotting.
In regard to serotonin within the brain, there are many symptoms that can be associated with low levels of this neurotransmitter:
- Down in mood or feeling depressed
- Feelings of anxiety
- Irritability and frustration
- Low self-esteem
- Problems with memory
- Poor appetite
- Issues with sleeping and insomnia in worse cases
Low levels of serotonin have been associated with some mental health conditions, such as mood disorders. As serotonin helps to regulate mood, people with low serotonin may have a low mood or a less stable mood without understand why this is.
If low moods persist because of low serotonin levels, this could result in depression. Depression is categorized as feelings of intense sadness, hopelessness, chronic fatigue, and suicidal thoughts.
wise, anxiety disorders can be attributed partly to low serotonin levels. For instance, obsessive-compulsive disorder (OCD) is an anxiety disorder in which an individual uses compulsive behaviors to deal with intrusive anxious thoughts.
Also, people who have schizophrenia, a condition in which individuals may experience unusual thoughts, develop delusions and experiencing hallucinations, has also thought to be related to low serotonin levels.
A cause of low levels of serotonin could be due to not producing enough of this neurotransmitter. An amino acid called tryptophan is essential for the production of serotonin.
This amino acid is only obtained from food, so if there is a deficiency of this, less serotonin will be made as a result. Similarly, vitamins B6 and D deficiencies have been linked to lower levels of serotonin.
Another cause of low serotonin levels can result from not having enough serotonin receptors in the brain, or the receptors not functioning properly.
When serotonin leaves the presynaptic neuron, it could be broken down in the synaptic cleft too quickly or it could be reabsorbed back into the presynaptic neuron too soon, stopping it from reaching the next neurons during neurotransmission.
Increasing Serotonin Levels
The occipital lobes can be divided into several functional areas, although there are no anatomical markers distinguishing these areas.
Brain imaging has revealed that neurons in the occipital cortex create an ongoing visual map of information taken in by the retinas.
Similarly, it is worth noting that the motor cortex plays a role in the muscles of the eyes, which are heavily relied on by the occipital lobes.
Often, medication is prescribed to individuals who wish to treat some of the symptoms or mental health conditions associated with low levels of serotonin. Below are some of the main types of medications and their functions:
Selective Serotonin Re-uptake Inhibitors (SSRIs)
The most prescribed antidepressant medication are selective serotonin re-uptake inhibitors (SSRIs).
These are used to treat conditions such as depression, anxiety, panic disorders, obsessive-compulsive disorders, and phobias. SSRIs work by blocking the re-uptake of serotonin from the neuron that released it.
Since the SSRIs are preventing serotonin being reabsorbed into the presynaptic neuron, there will more serotonin circulating around the synaptic cleft.
This makes it more ly that serotonin will reach the receptors of the postsynaptic neuron, so it will be able to influence the brain and increase mood as a result. Some types of SSRI include Citalopram (Celexa), Fluoxetine (Prozac), and Sertraline (Zoloft).
Tricyclic antidepressants (TCAs)
An older classification of antidepressant, tricyclic antidepressants (TCAs) work in a similar fashion to SSRIs in the sense that they also block the re-uptake of serotonin from returning to the presynaptic neuron.
However, TCAs also work by blocking the re-uptake of another neurotransmitter called norepinephrine (also known as noradrenaline), which also affects mood.
Despite working in a similar way to SSRIs, TCAs are known to not be as tolerable as SSRIs, having more side effects. Similarly, SSRIs have shown to be more effective than TCAs in terms of treating depression with anxiety (Lane, Baldwin, & Preskorn, 1995).
Monoamine oxidase inhibitors (MAOIs)
Another older classification of antidepressant are monoamine oxidase inhibitors (MAOIs).
Typically, when serotonin enters the synaptic cleft for neurotransmission, some of the neurotransmitter gets removed by an enzyme called monoamine oxidase. MAOIs, however, will work to prevent this from happening.
This ultimately means that there will be more serotonin circulating in the synaptic cleft, making it more ly that it will reach the receptors of the postsynaptic neuron.
MAOIs can also have an effect on other neurotransmitters in the brain which can cause unwarranted side effects. This type of antidepressant is not prescribed as much as SSRIs due to the side effects and because of associated dietary precautions that need to be taken when using the medication.
MAOIs could have adverse reactions when mixed with other drugs and in rare cases, can cause dangerously high levels of serotonin, known as serotonin syndrome.
Too Much Serotonin
Although serotonin is beneficial in maintaining a good mood and providing people with happy feelings, too much serotonin can be detrimental.
Having a surplus of serotonin in the brain can come as a result of the medications that are being taken to increase low serotonin levels.
Having too much serotonin in the brain can result in a condition called serotonin syndrome.
This syndrome can arise after starting to take a new medication, or when increasing the dosage of an existing medication.Some of the milder symptoms associated with serotonin syndrome are as follows:
- Dilated pupils
- Rapid heart rate
- High blood pressure
- Shivering and goose bumps
Mild cases of serotonin syndrome may go away within a day of stopping the medications causing the symptoms, although if not treated it could result in worsened symptoms such as seizures, irregular heartbeat, unconsciousness, or even death in the worse cases.
Therefore, if someone is considering taking medication for curing symptoms of low serotonin or associated mental health conditions, they would be advised to start off with a small dosage, before potentially increasing this.
Olivia Guy-Evans obtained her undergraduate degree in Educational Psychology at Edge Hill University in 2015. She then received her master’s degree in Psychology of Education from the University of Bristol in 2019. Olivia has been working as a support worker for adults with learning disabilities in Bristol for the last four years.
How to reference this article:
Guy-Evans, O. (2021, June 14). What is serotonin . Simply Psychology. www.simplypsychology.org/what-is-serotonin.html
APA Style References
Berger, M., Gray, J. A., & Roth, B. L. (2009). The expanded biology of serotonin. Annual review of medicine, 60, 355-366.
Lane, R., Baldwin, D., & Preskorn, S. (1995). The SSRIs: advantages, disadvantages and differences. Journal of psychopharmacology, 9(2_suppl), 163-178.
Mayo Clinic. (2019, October 8). Tricyclic antidepressants and tetracyclic antidepressants. https://www.mayoclinic.org/diseases-conditions/depression/in-depth/antidepressants/art-20046983
White, M. A. (2020, July 13). Serotonin deficiency: Symptoms and treatment. Medical News Today. https://www.medicalnewstoday.com/articles/serotonin-deficiency#symptoms
Scaccia, A. (2020, August 19). Serotonin: What You Need to Know. Healthline. https://www.healthline.com/health/mental-health/serotonin#takeaway
Salters-Pedneault, K. (2021, May 28). What Is Serotonin? Very well mind. https://www.verywellmind.com/what-is-serotonin-425327
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What Is Serotonin Syndrome? A Potential Danger of SSRIs
- Serotonin syndrome is a reaction to commonly prescribed antidepressants, painkillers, antibiotics, antihistamines, anti-nausea medications, migraine medications, and some herbal supplements.
- It’s more common in people who take one or more of these medications at the same time.
- Most people with serotonin syndrome have mild symptoms that resolve quickly, but those with severe cases need treatment in the hospital.
Serotonin is a chemical that affects mood and how the brain responds to things fear, anxiety, and stress. Many medications increase serotonin levels, including some commonly prescribed for nausea and pain.
Serotonin syndrome happens when serotonin levels are too high in the brain. While many cases of serotonin syndrome are mild, severe cases can be life-threatening. If you or a loved one takes medications that can cause serotonin syndrome, it can be helpful to know what to look out for.
Read more to learn how to recognize the symptoms of serotonin syndrome and what to do about it.
Serotonin syndrome, also called serotonin toxicity, is a condition caused by medications that increase serotonin levels in the brain. It’s not clear how many people get serotonin syndrome because most people with serotonin syndrome have mild symptoms and often don’t seek care.
What are the symptoms of serotonin syndrome?
Symptoms of serotonin syndrome vary depending on the severity of the condition. People with mild serotonin syndrome can experience:
- Tremor (mild shaking in the hands)
- Fast heart rate
- Trouble sleeping
People with severe serotonin syndrome have symptoms that are harder to ignore, such as:
- High fever
- Fast heart rate
- High blood pressure
- Lockjaw (trouble opening the mouth)
- Trouble turning around or getting up from a lying position
- Uncontrollable, spontaneous movements of their limbs (clonus, myoclonus)
- Unusual eye movements (ocular clonus)
All medications that increase serotonin in the brain can cause serotonin syndrome. But, because they are so widely used, this occurs most commonly with selective serotonin reuptake inhibitors (SSRIs) and selective serotonin-norepinephrine reuptake inhibitors (SNRIs).
Other medications can cause serotonin syndrome too. But, remember that taking any one of these medications on its own and at the recommended dose is unly to be a problem. Most cases of serotonin syndrome happen when people take large doses of multiple medications that release serotonin. Here’s a (non-exhaustive) list of some common culprits.
Antidepressants are the most common medications that cause serotonin syndrome.
Monoamine oxidase inhibitors (MAOIs) aren’t used much anymore to treat depression, but they are the most ly to cause serotonin syndrome. MAOIs include:
SSRIs and SNRIs are much more commonly prescribed to treat depression and anxiety. These medications are less ly to cause serotonin syndrome, but it is possible, especially in people taking high doses in combination with other medications or supplements that release serotonin.
Common examples of SSRIs and SNRIs include:
- Citalopram (Celexa)
- Desvenlafaxine (Pristiq)
- Duloxetine (Cymbalta)
- Escitalopram (Lexapro)
- Fluoxetine (Prozac)
- Levomilnacipran (Fetzima)
- Paroxetine (Paxil)
- Sertraline (Zoloft)
- Venlafaxine (Effexor)
- Vortioxetine (Trintellix)
- Vilazodone (Viibryd)
Some people use supplements to treat depression and mood disorders. Taking certain supplements along with prescription antidepressants can cause serotonin syndrome. Supplements that can cause release serotonin include:
- St. John’s wort
Antibiotics, antifungals, and antivirals
Antimicrobials can cause serotonin syndrome when used by people who are also taking an SSRI or SNRI. Be careful with antibiotics, antifungals, and antiviral medications, such as:
People taking SSRIs and certain pain medications have developed serotonin syndrome. Pain medications that increase serotonin levels in the brain include:
Anti-nausea medications can also increase serotonin levels. People taking SSRI/SNRIs should be careful when using:
Medications called triptans, sumatriptan and zolmitriptan, are used to treat migraine headaches. They can cause serotonin syndrome when taken with SSRI/SNRIs. In 2006, the FDA warned that combining these two types of medications could cause severe serotonin syndrome.
Two antihistamines that raise serotonin levels in the brain are:
Nearly all of the dextromethorphan-related serotonin syndrome cases happened because people took dextromethorphan and another serotonin-releasing medication.
Serotonin syndrome is a clinical diagnosis meaning the diagnosis is your symptoms and what a healthcare provider observes. There aren’t any blood tests or scans that can confirm the diagnosis of serotonin syndrome.
Since people can have a wide range of symptoms, healthcare providers sometimes use tools to help determine if someone is having mild or severe symptoms.
One tool healthcare providers use is called the Hunter Serotonin Toxicity Criteria (HSTC).
If someone stops taking the serotonin-releasing medication, symptoms from mild serotonin syndrome will go away on their own after 24-72 hours. People with mild symptoms should stay in touch with their healthcare providers but in general they don’t need any other treatment.
People with moderate to severe symptoms will need treatment.
The first treatment for serotonin syndrome is to stop taking any serotonin-releasing medications. Stopping SSRI/SNRIs suddenly can cause other symptoms so only stop these medications under supervision from a healthcare provider. In cases where someone needs to go to the hospital, they may receive treatment to stabilize their condition, such as:
- Intravenous (IV) fluids
- Oxygen therapy
- Medications including benzodiazepines and cyproheptadine which help counteract the effects of excess serotonin
Severe cases of serotonin syndrome are a medical emergency and can occasionally cause death.
If you take serotonin-releasing medications make sure you:
- Always point this out to your prescriber and pharmacist
- Avoid taking more than one serotonin-releasing medication at a time
- Use serotonin-releasing medications as prescribed by your healthcare provider, and avoid taking extra doses
- Check with your healthcare provider before starting over-the-counter medications or supplements to make sure they don’t increase serotonin levels
Serotonin syndrome is caused by medications that increase the amount of serotonin in the brain. Most cases are mild and go away within 24-72 hours after stopping the medication. However, some people have severe cases and require hospitalization. People who only take one serotonin-releasing medication at the recommended dose don’t usually develop serotonin syndrome.
Serotonin Syndrome: Symptoms, Causes, Treatments
Serotonin syndrome is a condition that happens when there is too much serotonin in the body. This can be caused by medications that impact serotonin levels. Antidepressants are linked to this condition. Serotonin Syndrome
Serotonin is a neurotransmitter. Neurotransmitters are chemicals used by your body’s nerve cells. These chemicals send signals that tell your body how to work.
Serotonin affects the brain and other body systems. It plays a role in many body functions. It affects your mood, sleep habits, and even how hungry you are.
Continuing research seeks to understand serotonin’s role. Low serotonin levels may be linked to depression.
What is serotonin syndrome?
Serotonin syndrome is sometimes called serotonin toxicity. The condition happens when people experience symptoms from having too much serotonin in the body.
Doctors first recognized serotonin syndrome in the 1960s, after the introduction of the first antidepressant medications. Today, more serotonin-affecting (serotonergic) medications are becoming available. At the same time, the incidence of serotonin syndrome appears to be increasing.
Most people can safely take serotonin-affecting medication under the guidance of a medical professional. Serotonin-affecting medications are commonly prescribed and effectively treat depression. When someone’s body processes serotonin differently (or it can’t process a large amount of serotonin), serotonin syndrome symptoms can occur.
A rise in serotonin levels can cause serotonin syndrome. This increase in serotonin can happen when a person:
- Takes more than one medication that affects serotonin levels.
- Recently started on a medication or increased the dose of a medication known to increase serotonin levels.
- Takes too much of one serotonin-related medication, accidentally or on purpose.
Antidepressants are the most familiar medications that affect serotonin levels. Different classes of antidepressants include:
- Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac®), citalopram (Celexa®), and sertraline (Zoloft®).
- Serotonin and norepinephrine inhibitors such as duloxetine (Cymbalta®) and venlafaxine (Effexor®).
- Bupropion (Wellbutrin®).
- Tricyclic antidepressants such as amitriptyline (Elavil®) and nortriptyline (Pamelor®).
Several other medications can affect the body’s serotonin use. These medications treat:
- Severe pain: This pain is treated with medications including opioids tramadol and oxycodone.
- Coughing: Over-the-counter (OTC) cough and cold medications containing dextromethorphan can be used to treat coughing.
- Migraine headaches: These headaches can be treated with medicines called triptans.
- HIV/AIDS: Drugs ritonavir can be used to treat HIV/AIDS.
- Anti-nausea medications: Metoclopramide (Reglan®) and ondansetron (Zofran®).
Other factors may affect how your body regulates serotonin levels. These factors include using:
- Herbal supplements: These can include ginseng and St. John’s wort. Avoid using these supplements along with a prescribed SSRI.
- Illegal substances: These substances include ecstasy, hallucinogen LSD, and cocaine.
Medical experts still have much to learn about serotonin syndrome. Not all doctors know the signs. If you have concerns about the serotonin-affecting medications you take, bring them up to your doctor.
What are the most common serotonin syndrome symptoms?
Serotonin syndrome symptoms may be mild or severe. Symptoms may start soon after you take a new medication or increase the dose. Symptoms can occur within hours.
Some cases of serotonin syndrome can be life-threatening. People need quick treatment for the condition. If you are taking a medication that affects serotonin and experience any of the following symptoms, call your doctor or visit an urgent or emergency care facility right away:
- Mood changes, such as irritation or confusion
- Dilated pupils.
- Arrhythmia (a fast or abnormal heartbeat)
- Muscle stiffness, especially in the legs
- Sweating or shivering
- Increased heart rate and increased blood pressure
No available test can identify serotonin syndrome. To make a diagnosis, doctors consider your symptoms and all the medications you are taking. These include prescribed medicines, over-the-counter medicines, and any other supplements or drugs.
Doctors may need your input to diagnose serotonin syndrome. It’s important to be honest about the medications you take and your recent activities.
Some people have similar symptoms with a condition called neuroleptic malignant syndrome (NMS). NMS is a rare but serious reaction to antipsychotic medications such as haloperidol and fluphenazine. If you develop fever, muscle stiffness, or confusion after taking an antipsychotic medication, you should call your doctor right away.
In mild cases, stopping a medication or changing your dosage may make your symptoms go away. Your body’s serotonin levels may go back to normal within a few days. Do not change medications without a doctor’s advice.
Doctors may prescribe medications that stop your body from producing serotonin. These medications can help relieve symptoms.
If you do not treat the symptoms, serotonin syndrome can be serious. In some cases, the condition may be life-threatening. Some people need treatment in a hospital, where they can be watched closely.
Anyone who takes a substance (medication or otherwise) that affects the body’s serotonin levels could be at risk for serotonin syndrome.
It’s important to keep close tabs on all medications you take. It’s also important to talk with your doctor regularly. These precautions can help you spot signs of serotonin syndrome early. Early identification may help you avoid more severe symptoms.
You have a higher risk of developing serotonin syndrome symptoms if you:
- Take more than one serotonergic medication, such as an antidepressant and cough medicine.
- Recently increased dosage of a serotonergic medication.
- Use St. John’s wort or ginseng.
- Use certain illegal drugs.
In severe cases, serotonin syndrome can affect how vital body systems function. Serotonin syndrome may even lead to a loss of consciousness (fainting or passing out).
See a doctor right away if you believe you may have signs of serotonin syndrome. Take extra caution if you have risk factors for the condition.
Last reviewed by a Cleveland Clinic medical professional on 01/15/2018.
Serotonin: What to Know
Serotonin is a hormone and a neurotransmitter that is involved in the function of several different organ systems in the body.
A Happy Chemical: Serotonin and Mood
Serotonin is sometimes known as the happy chemical, because it appears to play an important role in regulating mood, and low levels of serotonin in the brain have been associated with depression. (1)
While there’s a link between low levels of serotonin and depression, it’s not clear whether low serotonin levels cause depression or whether depression causes a drop in serotonin levels. (1)
As a neurotransmitter, serotonin sends messages between nerve cells in the brain. That makes serotonin an important molecule for influencing mental health and brain function.
The Role of Serotonin in Brain Function
In addition to depression, serotonin may play a role in other brain and mental health disorders, including anxiety disorder, obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), phobias, and even epilepsy.
Serotonin plays an important role in many other body functions, too. It’s involved in appetite and digestion (bowel function and bowel movements), bone health, sex, and sleep.
Serotonin is a precursor to melatonin, a chemical that helps regulate the body’s sleep-wake cycle. (2) Certain antidepressants that raise serotonin levels have been associated with sexual dysfunction.
Too high or too low levels of serotonin have been linked to diseases such as irritable bowel syndrome (IBS), heart disease, and osteoporosis — a disease that weakens the bones — according to an article published in April 2016 in the journal Cell. (3)
Gut Bacteria and Serotonin Production
In recent years, scientists have found that gut bacteria help to produce serotonin and that most of the body’s supply of serotonin can actually be found in the lining of the stomach and intestines. (3)
It’s not clear yet whether — or how — altered serotonin levels in the gut influence brain activity. Some researchers have postulated that serotonin in the gut may stimulate the vagus nerve, the long nerve that connects the digestive tract to the brain. (4)
Selective Serotonin Reuptake Inhibitors (SSRIs)
Selective serotonin reuptake inhibitors, or SSRIs, are a class of drugs used to treat depression and anxiety. They’re the most popular class of antidepressants. (5)
Commonly prescribed SSRIs include:
How Do SSRI Drugs Work?
SSRIs are thought to work by increasing serotonin levels in the brain. SSRIs do this by blocking the absorption of serotonin by nerve cells, keeping more of it available for passing along further messages between nerve cells in the brain.
Other groups of antidepressants, called serotonin and norepinephrine reuptake inhibitors (SNRIs) and serotonin-norepinephrine-dopamine reuptake inhibitors (SNDRIs), block the absorption of serotonin and the other neurotransmitters norepinephrine and dopamine. (5)
SSRIs are sometimes called second generation antidepressants. In general, these antidepressants have fewer side effects than older tricyclic antidepressants.
Still, there are still several common side effects associated with SSRI use. These may include: (6)
- Dry mouth
- Nervousness (jitters)
- Weight gain
- Sexual dysfunction
Some people — especially children, teens, and young adults — may have an increase in suicidal thoughts while taking SSRIs.
These side effects are most common when people first start to take SSRIs — or when they change a dose — and tend to lessen over time.
Who Benefits From Use of SSRIs?
SSRIs appear to work best for people with major or severe depression.
A review of studies published in April 2018 in the journal The Lancet found that most antidepressants, including commonly prescribed SSRIs, offered a modest benefit over a placebo treatment for people with major depressive disorder.
(7) According to the U.S. National Library of Medicine, antidepressants, including SSRIs, helped to relieve depression symptoms in about 20 percent of people. (8)
The benefits of SSRIs for people with mild to moderate depression remain unclear.
Some researchers have shown that SSRIs are most effective when they are combined with talk or behavior therapies that help depression sufferers learn new strategies for coping with troublesome thoughts. A study published in June 2018 in the journal Nature Communications suggested that serotonin may help to speed learning, which could help to explain these findings. (9)
Serotonin Foods and Supplements
Serotonin isn’t found in foods, but its precursor, tryptophan, is. Tryptophan is an essential amino acid that is important in the production of serotonin. Amino acids are the building blocks of protein.
Scientists have shown that the tryptophan in the diet is linked to levels of serotonin in the brain, with lower amounts of dietary tryptophan causing brain levels of serotonin to drop, according to a review published in January 2016 in the journal Nutrients. (10)
Tryptophan is present in most protein-rich foods. Foods high in tryptophan include:
- Nuts and seeds
- Turkey and other poultry
- Soy foods
Some studies have proposed that eating tryptophan-rich foods may increase levels of serotonin in the brain and help treat depression symptoms. Other studies have found no correlation between tryptophan-rich foods or supplements and depression symptoms, according to a review published in January 2016 in the journal Current Opinion in Clinical Nutrition and Metabolic Care. (11)
Most research indicates that any serotonin boost you might get from eating high-tryptophan foods is probably small. That’s because foods rich in tryptophan tend to be rich in other amino acids as well — and these molecules all have to compete with one another to be absorbed into the brain. (11)
The dietary supplement 5-HTP (5-hydroxytryptophan), a chemical by-product of tryptophan, also helps to increase serotonin production in the brain. (12)
According to the Natural Medicines Comprehensive Database, the dietary supplement may be effective in reducing symptoms of depression in some people. (12)
But larger studies are needed to prove that 5-HTP is safe and effective, and to date 5-HTP has not been approved by the Food and Drug Administration (FDA) as a treatment for depression.
In addition, 5-HTP should not be taken with antidepressant drugs or other depression medication. Many drugs taken for depression or anxiety also raise serotonin levels, and increasing serotonin levels too much can cause serious side effects, including heart problems. (12)
Serotonin syndrome, also called serotonin toxicity, is a rare but potentially life-threatening condition that can happen when serotonin levels are too high. (13)
Serotonin syndrome is most ly to occur when starting an antidepressant medication, increasing the dosage of an antidepressant medication, or when two drugs that raise the body’s levels of serotonin are taken at the same time, causing too much serotonin to accumulate in the brain.
Serotonin-raising medicines include: (14)
If you take any of these medicines, be sure to read the packaging labels for warnings about the potential risks of serotonin syndrome. Talk to your doctor if you have any concerns.
Symptoms of serotonin syndrome usually occur within minutes to hours. They may include: (14)
- Rapid heartbeat or fast pulse
- High blood pressure
- Heavy sweating
- Rapid breathing
- Agitation or restlessness
- Hot, dry skin
- Shivering, goose bumps
- Dilated pupils
- Nausea and vomiting
- Rigid muscles, twitching
- Loss of coordination
Call your healthcare provider immediately if you think you may be experiencing symptoms of serotonin syndrome. Symptoms may vary from mild to severe. Patients with severe serotonin syndrome may require hospitalization in an intensive care unit.