Celexa is in a class of medicines called Selective Serotonin Reuptake Inhibitors (SSRIs) used to treat depression. Celexa has been linked to a life-threatening condition called serotonin syndrome, and the FDA has issued a number of public advisories on the risk of suicidal thoughts in users of SSRIs like Celexa. This section contains health and legal information on Celexa.