Lexapro (escitalopram) is an antidepressant belonging to a group of drugs called selective serotonin reuptake inhibitors (SSRIs). Escitalopram affects chemicals in the brain that may become unbalanced and cause depression or anxiety.Lexapro is used to treat anxiety in adults. Lexapro is also used to treat major depressive disorder in adults and adolescents who are at least 12 years old.