SLC6A4 and Anxiety: In particular, the artificial increase in the concentration of serotonin using 5-HT transporters (SERT) or monoamine oxidase (MAO) inhibitors, and 5-HT agonists such as 5-MT, induces several brain disorders, for instance, affective-abnormalities, cognitive and fear extinction deficiencies, anxiety-like behaviors [36,37], changes in the expression of 5-HT receptors [38,39,40], abnormalities in the laminar and columnar organization [41,42,43] and the excitability of areas such as the PFC [44].