Serotonin is one of the four main neurotransmitters in the brain and body, along with acetylcholine, dopamine, and the neurotransmitter GABA. When there is a deficiency of serotonin, the body usually responds with a depressive state, but it can also have excess of this chemical in our body, causing what is called serotonin syndrome .

What is serotonin

Serotonin is one of the four chemicals that carry signals along the nerves. Hence the name neurotransmitter. The 80 to 90 percent of serotonin is in the gastrointestinal tract or gut, and is crucial for the brain and body functions.

The chemical is created through biochemical conversion. The building block of serotonin is tryptophan , which is also the building block of protein. Tryptophan binds with hydroxylase, which creates a chemical reaction that produces 5-hydroxytryptamine (5-HTP), also known as serotonin .

Why Serotonin Is Important

Serotonin is important for a variety of reasons. It is known primarily for its role in regulating mood, but it also helps normalize appetite, digestion, social behavior, and sleep. Cognitively, serotonin primarily affects learning and memory functions.

Also, serotonin is known as an important chemical for happiness and well-being , which is what comes in most people’s minds.

What if we are deficient in serotonin

Being an important chemical for sending and receiving nerve signals, a lack of serotonin disrupts internal “communication”. It is this disruption that causes the various adverse psychological effects, such as depression, decreased sexual desire and function, as well as disrupted sleep, memory, and learning.

Outside of the brain, serotonin affects the functioning of the cardiovascular system, the endocrine system, and various muscles. There is some evidence that a defect within the serotonin system could be an underlying cause of SIDS (sudden infant death syndrome).

Serotonin syndrome

Serotonin syndrome is the mirror opposite to serotonin deficiency . As mentioned, it is serotonin deficiency that causes depression. It is important to remember this point, since deficiency is much more widespread than serotonin syndrome.

Again, serotonin deficiency = depression, and excessive serotonin = other illnesses (or Serotonin Syndrome.)

Serotonin syndrome on the other hand occurs when there is an excessive amount of nerve cell activity, which can be a fatal condition.

What Causes Serotonin Syndrome

Serotonin syndrome can occur if you are taking certain medications known to affect serotonin production. The highest risk of serotonin syndrome occurs if you are taking two or more medications and / or supplements that influence serotonin. Most often, serotonin syndrome occurs when someone starts a drug or increases the dose.

Prescription drugs are the main cause of serotonin syndrome. The most commonly prescribed class of medications that affect serotonin levels are antidepressants.


SSRIs, or selective serotonin reuptake inhibitors, work by blocking the reuptake of the chemical in the brain by increasing the amount of serotonin available. SSRIs are “selective” in the sense that they do not affect other neurotransmitters.

Los ISRS comunes incluyen Citalopram (Celexa), Escitalopram (Lexapro), Fluoxetine (Prozac), Paroxetine (Paxil o Pexeva), Sertraline (Zoloft) y Vilazodone (Viibryd).


SSRIs or serotonin and norepinephrine reuptake inhibitors (nor-ep-ih-NEF-rin), act by blocking the reuptake of serotonin and norepinephrine. Deficiencies in the latter chemical can leave you feeling fatigued and mentally hazy, with little interest in life.

SSRIs are a treatment option when a patient does not respond to SSRIs, something that occurs in about half of the people diagnosed with depression.

Common SSRIs include: Desvenlafaxine (Pristiq, Khedezla), Duloxetine (Cymbalta), Levomilnacipran (Fetzyme), and Venlafaxine (Effexor and Effexor XR).

Other medications

Here are some other prescription and over-the-counter medications that can raise serotonin levels or increase the risk of serotonin syndrome:

Monoamine oxidase inhibitors (MAOIs), pain relievers, migraine medications, nausea medications, cough suppressants (mostly Dextromethorphan), and illegal drugs (LSD, cocaine) and certain supplements (St. John’s wort and ginseng).

Serotonin precursors

As mentioned, serotonin is produced through biological reaction within the body. It is important to mention some “precursors” or “other things” (supplements, vitamins, minerals, etc.) that can increase serotonin levels.

Here are some things known or thought to increase the chemical in the blood: vitamins B6 and B12, vitamins C and D, folate, magnesium, DHA (in fish oil), inositol, normal thyroid function, and vigorous exercise.

Why know this

  • This is important to know because depression is one of the most common medical conditions in the world.
  • More people are diagnosed with depression (and anxiety) than anyone else.
  • Serotonin deficiency is a potentially fatal condition.
  • Because we have a health care system known to overprescribe antidepressants (and other prescription drugs). While these drugs may be helpful to some, others face the risk of dependence or worse.

Symptoms of serotonin syndrome

The symptoms of serotonin syndrome often begin in a few hours after taking a new medication that affects serotonin levels or excessively increase the dose you are already taking.

These are some of the most common signs of serotonin syndrome, if you experience a combination of any of the above symptoms seek medical attention immediately.

  • Confusion
  • Headache
  • Nausea, diarrhea and / or vomiting
  • Temblor
  • Loss of muscle coordination
  • Shivering and / or profuse sweating
  • High fever (life-threatening)
  • Seizures (life-threatening)
  • Loss of consciousness (life-threatening
  • Irregular heartbeat (life threatening)

By Dr. Eric Jackson

Dr. Eric Jackson provides primary Internal Medicine care for men and women and treats patients with bone and mineral diseases, diabetes, heart conditions, and other chronic illnesses.He is a Washington University Bone Health Program physician and is a certified Bone Densitometrist. Dr. Avery is consistently recognized in "The Best Doctors in America" list.

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