To treat anxiety and major depressive disorder. Lexapro is an astonishing antidepressant medication that can help many types of depression and helps depressed individuals live the kind of life that non-depressed people take for granted. Lexapro blocks the re-absorption of serotonin by the first nerve cell. Lexapro side effects are unlikely, but seek immediate medical attention if Lexapro side effects occur. If left untreated, can cause major problems in your life.