Zoloft is prescribed for major depressive disorder--a persistently low mood that interferes with everyday living. Symptoms may include loss of interest in your usual activities, disturbed sleep, change in appetite, constant fidgeting or lethargic movement, fatigue, feelings of worthlessness or guilt, difficulty thinking or concentrating, and recurrent thoughts of suicide.

Zoloft is also used in the treatment of obsessive-compulsive disorder--symptoms of which include unwanted thoughts that won't go away and an irresistible urge to keep repeating certain actions, such as hand-washing or counting. It is also prescribed for the treatment of panic disorder (unexpected attacks of overwhelming anxiety, accompanied by fear of their return), and for posttraumatic stress disorder (re-experiencing a dangerous or life-threatening event through intrusive thoughts, flashbacks, and intense psychological distress).

Zoloft is a member of the family of drugs called "selective serotonin re-uptake inhibitors." Serotonin is one of the chemical messengers believed to govern moods. Ordinarily, it is quickly reabsorbed after its release at the junctures between nerves. Re-uptake inhibitors such as Zoloft slow this process, thereby boosting the levels of serotonin available in the brain.