Well, they are... It is literally considered a mental illness in the DSM-5 Archive: https://archive.today/hZKuq From the post: >>Peru has officially classified trans people as 'mentally ill'. Under the decree signed by President Dina Boluarte, 'transsexualism, dual-role transvestism, gender identity disorder in childhood, other gender identity disorders and fetishistic transvestism' are now all recorded as mental illnesses. The move, which comes just days before the 34-year anniversary of the World Health Organisation's removal of homosexuality from the list of International Classification of Diseases (ICD), has prompted fury from rights groups.