Zoloft (sertraline) is an antidepressant used to treat depression. It is also used to treat social anxiety disorder, post-traumatic stress disorder, panic disorder, premenstrual dysphoric disorder (PMDD), and obsessive compulsive disorder (OCD). Zoloft belongs to a group Side effects of synthroid medicines called selective serotonin reuptake inhibitors (SSRIs). It works by increasing the serotonin levels in your brain