Serotonin is a chemical produced by the body that acts on the nervous system and is associated with feelings of well-being. Researchers have extensively studied the role of serotonin in mood disorders such as anxiety and depression. According to a review published in the "Journal of Psychiatry and Neuroscience" in 2007, experts in the field have linked changes in serotonin with changes in mood. Scientists' understanding of the role of serotonin in anxiety is constantly evolving.
Also known as 5-hydroxytryptophan, serotonin is part of a class of molecules called neurotransmitters and is derived from the amino acid tryptophan. According to Encyclopedia Britannica, serotonin is found in the brain, intestines, blood platelets and cells of the immune system called mast cells. Its highest concentrations are in regions of the brain called the hypothalamus and the midbrain. Changes in serotonin concentration in these regions are associated with changes in mood.
The brain and nervous system are made up of cells called neurons, which communicate with one another using neurotransmitters such as serotonin. Neurotransmitters like serotonin are secreted by one neuron into a cell junction called a synapse. There, the serotonin binds to structures called receptors attached to a second neuron. The receptors allow that adjacent neuron to take up serotonin, leading to chemical changes in other parts of the cell that regulate brain function. Altered mood states may result from the cell either taking up too much or not enough serotonin.
The Roots of Anxiety
There are 14 different serotonin receptors, but the one most commonly studied in its relationship with anxiety is the 5-HT1A receptor. The results of an experiment with mice published in "Neuropsychopharmacology" in August 2013 demonstrated that mice without a 5-HT1A receptor early in life showed increased anxiety in adulthood. Additionally, mice exposed to stress in early life also developed anxiety in adulthood, but the stress exposure had no additional effect on mice who were missing the 5-HT1A receptor. The researchers claim that their evidence suggests a relationship between receptor levels in youth and susceptibility to anxiety in adulthood.
Keys to Medication
Serotonin and its receptor, when bound together, fit like a key into a lock. The May 2013 issue of "Science" reported that scientists at University of North Carolina Chapel Hill Medical School discovered the structure of the receptor and this lock and key relationship. Like serotonin itself, anti-anxiety medications can also bind to those receptors to regulate levels of serotonin, and knowing the structure of the receptor allows researchers to better understand how the medications work. They explain that this is a huge step forward in developing new medications to combat anxiety and depression.