Gender dysphoria or gender identity disorder (GID) is the formal diagnosis used by psychologists and physicians to describe people who experience significant dysphoria (distress) with the sex and gender they were assigned at birth. Evidence suggests that people who identify with a gender different from the one they were assigned at birth may do so not just due to psychological or behavioral causes, but also biological ones related to their genetics, the makeup of their brains, or prenatal exposure to hormones.