2.19 What is Serotonin? – Definition & Function

Jan 18, 2020 | ch2 Biological Bases of Behaviour, Courses, Intro to Psychology

This lesson describes what serotonin is and how it is used in the body. In addition, we’ll discuss SSRIs, which boost serotonin levels in the brain; side effects of using SSRI’s; serotonin syndrome; and natural ways to boost serotonin in the body.

Definition of Serotonin

Serotonin is a chemical that is manufactured in the body and acts as a neurotransmitter. A neurotransmitter is a chemical that helps signals cross from one neuron, or nerve cell, to the other. Although most people who have any knowledge of serotonin know that it is one of the brain chemicals responsible for regulating people’s moods, what many people don’t know is that 80-90% of serotonin is manufactured and lives in the gastrointestinal tract, or in short, our digestive system! So, even though it is widely believed to be a ‘brain chemical,’ serotonin lives primarily in our stomach and intestines, where it helps to regulate gastric functions.

The Uses of Serotonin

Serotonin was discovered by Maurice Rapport in 1948, so it’s relatively ‘new’ in terms of what we know about it. It is widely believed by the medical community, though, that serotonin is definitely responsible to help regulate our moods, social behavior, appetite and digestion, sleep, memory, and sexual function. Therefore, it has a wide variety of functions that keep humans happy and on track.

The biggest news about serotonin that you’ve probably heard is its relationship to depression. While there is an almost-certain link between the two, what scientists don’t know is if low levels of serotonin in the brain cause depression, or if depression causes lower levels of serotonin. Nobody knows for sure. What scientists and doctors do know, however, is that selective serotonin reuptake inhibitors, or SSRIs for short, are a type of drug that can help tremendously with depression in many people.

Unfortunately, scientists don’t know exactly why these particular drugs work. Despite this, SSRIs are the most widely prescribed type of antidepressants in the world and are approved by the Food and Drug Administration (FDA) specifically to treat depression. One thing that is known, however, is how SSRIs work. Under normal circumstances, serotonin transmits its neural information from neuron to neuron in the brain, and then it is reabsorbed by the body. When a patient is taking SSRIs, however, the reabsorption by the body is prevented, so the amount of serotonin in the brain increases. This is thought to cause the patient to feel better and less depressed. Interestingly, the drugs MDMA and cocaine work the same way, which is what causes users to feel high.

SSRIs, as with any type of drug, can cause side effects when taken. The following side effects may be a result of more serotonin being produced:

  • Diarrhea
  • Dizziness
  • Agitation
  • Dry mouth
  • Headaches
  • Loss of appetite
  • Loss of sex drive
  • Insomnia
  • Nausea or vomiting
  • Weight gain or weight loss

Serotonin Syndrome

Sometimes the central nervous system is stimulated too much, and as a result, there is too much serotonin in the body, leading to something called serotonin syndrome. This can be caused by taking SSRIs along with other medications that incidentally increase serotonin levels. Here are the symptoms of serotonin syndrome:

  • Agitation
  • Confusion
  • Loss of muscle coordination
  • Sweating
  • Increased heart rate
  • Increased blood pressure
  • Pupil dilation

If you are taking SSRIs and experience any of these symptoms, it could be a sign of serotonin syndrome, and you should call your doctor immediately, as some of these symptoms can be very dangerous!

Other Ways to Affect Serotonin

Aside from taking SSRIs, there are natural ways to boost serotonin levels within the body. One of these ways is exercising. Exercise is a natural antidepressant, as it boosts the levels of serotonin and several other chemicals in the body that are related to mood. Eating a balanced diet with foods that are high in tryptophan (turkey is a food that is well-known for its abundance of tryptophan) is another way of boosting serotonin levels. Finally, light therapy, which has been shown to be effective in treating other mood disorders, is also beneficial. When a patient receives light therapy, he or she is exposed to a bright ultraviolet light. This can last from several minutes up to a couple of hours. Light therapy has been shown to help people who need a serotonin boost.

Lesson Summary

Serotonin is a naturally-occurring chemical in the body, and it is related to our moods and feelings of well-being. Antidepressants called SSRIs are widely prescribed and have been used for several decades to boost serotonin levels in the brain, which have a positive effect on mood. Although we don’t know exactly why SSRIs work, we know how they work in the brain. As with any drug, taking SSRIs has side effects. In addition to these side effects, too much serotonin can cause a dangerous condition called ‘serotonin syndrome.’ Aside from taking antidepressants, natural ways to boost serotonin levels in the body include diet, exercise, and light therapy.

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