Cymbalta (Duloxetine) is an antidepressant in a group called selective serotonin and norepinephrine reuptake inhibitor (SNRI) used to treat depression. . Cymbalta affects the chemicals in the brain that may become unbalanced and cause depression. Cymbalta is used to treat major depressive disorder and general anxiety disorder. It may also be used to treat certain types of nerve pain.