Excess Serotonin

Q Does the body automatically monitor serotonin levels and eliminate superfluous amounts to prevent the levels from becoming too high? What are the effects of too much serotonin?

— FRAN, Glen Waverley, VIC, Australia

A Yes, it does. Through the complex processes of downregulation and upregulation, the body maintains balanced levels of neurotransmitters under normal conditions. Bear in mind that tryptophan—the precursor of serotonin, one of our most important neurotransmitters—is an essential amino acid that we must ingest in our diets. However, as we age and especially when we are under stress, we use serotonin more rapidly, and for that reason, it is a good idea to supplement with tryptophan.

Serotonin is best known for its key role (along with noradrenaline and dopamine) in the regulation of mood and of emotions, such as fear and pleasure. (It is also, however, involved in learning and memory.) Deficiencies of this vital compound are known to be associated with aggressive behavior, depression, and even suicide.

Serotonin syndrome is a clinical condition arising from a drug-induced increase in intrasynaptic serotonin levels; it results primarily in overactivation of serotonin receptors in the central nervous system. A wide variety of symptoms is associated with serotonin syndrome, including tachycardia, restlessness, and anxiety, depending on its severity.1

This condition was far more common several decades ago when antidepressants known as MAO inhibitors were widely used. By itself, the use of supplemental tryptophan (or its immediate precursor, 5-HTP) has never been connected to serotonin syndrome.


  1. Frank C. Recognition and treatment of serotonin syndrome. Can Fam Physician 2008 Jul;54(7):988-92.

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