Serotonin is a chemical that transmits messages between brain cells, also known as a neurotransmitter. Serotonin is involved in the regulation of many functions including sleep, appetite, and mood, and a deficiency of serotonin has been linked to mental health problems such as depression and anxiety. A group of medications known as selective serotonin reuptake inhibitors (SSRIs), which increase the level of serotonin available within the central nervous system, are considered the first-line medication treatment for social anxiety disorder (SAD).

