Serotonin is a type of neurotransmitter that is found mainly in the central nervous system and the gastrointestinal (GI) tract. Much of the serotonin is located in the GI tract where it is used to regulate digestion. In the CNS, serotonin helps regulate mood, sleep, appetite, learning and memory.
Some of the most commonly prescribed antidepressant and anti-anxiety medications are those that impact serotonin levels. Selective serotonin reuptake inhibitors (SSRIs) work by inhibiting the reuptake of serotonin in one sell, which then increases the amount of serotonin available to the receptor cells.