Gender dysphoria—formerly known as “gender identity disorder”—is characterized by a severe and persistent discomfort in one’s biological sex.8 It typically begins in early childhood—ages two to four—though it may grow more severe in adolescence. But in most cases—nearly 70 percent—childhood gender dysphoria resolves.9 Historically, it afflicted a tiny sliver of the population (roughly .01 percent) and almost exclusively boys. Before 2012, in fact, there was no scientific literature on girls ages eleven to twenty-one ever having developed gender dysphoria at all.
