Celexa is used to treat major depression--a stubbornly low mood that persists nearly every day for at least 2 weeks and interferes with everyday living. Symptoms may include loss of interest in your usual activities, insomnia or excessive sleeping, a change in weight or appetite, constant fidgeting or a slowdown in movement, fatigue, feelings of worthlessness or guilt, difficulty thinking or concentrating, and repeated thoughts of suicide.

Like the antidepressant medications Paxil, Prozac, and Zoloft, Celexa is thought to work by boosting serotonin levels in the brain. Serotonin, one of the nervous system's primary chemical messengers, is known to elevate mood.