Serotonin Syndrome Explained Serotonin syndrome, also known as 5-HT syndrome, is a rare and potentially fatal condition caused by abnormally high levels of the neurotransmitter serotonin in the brain. In some studies, at least 14% to 16% of patients who overdose on selective serotonin reuptake inhibitors suffer from serotonin syndrome. The neurotransmitter serotonin is involved in regulating mood, […]