According to the criteria of ICD-10 (International Classification of Diseases according to the World Health Organization), transsexuality is a form of gender identity disorder. Transsexuality is present when a person physically clearly belongs to the male or female sex, but feels in his sensation to belong to the respective other sex and tries to approach this also physically as well as possible.
Clinical-psychological diagnostics and clinical-psychological treatment have been included in the recommendations for the treatment process for gender dysphoria or transsexualism since 2014. The Federal Ministry of Health has issued recommendations on the treatment process for gender dysphoria or transsexualism.