Zoloft (sertraline) is an antidepressant in a group of drugs called selective serotonin reuptake inhibitors (SSRIs). The way sertraline works is still not fully understood. It is thought to positively affect communication between nerve cells in the central nervous system and/or restore chemical balance in the brain. Zoloft is used to treat depression, obsessive-compulsive disorder, panic disorder, anxiety disorders, post-traumatic stress disorder (PTSD), and premenstrual dysphoric disorder (PMDD).