Sertraline is an antidepressant in the SSRI class that is prescribed to treat conditions like depression, anxiety, PTSD, and panic attacks. Like other medications, sertraline can cause side effects that range from mild to severe. Common side effects include nausea, insomnia, sexual problems, diarrhea, dizziness, dry mouth, fatigue, drowsiness, and loss of appetite. Rare but serious side effects should be reported right away and include suicidal thoughts, aggression, unusual behavior changes, and signs of an allergic reaction or serotonin syndrome.