For natal adult males, prevalence ranges from 0.005% to 0.014%, and for natal females, from 0.002% to 0.003%. Since not all adults seeking hormone treatment and surgical reas- signment attend specialty clinics, these rates are likely modest underestimates. Sex differ- ences in rate of referrals to specialty clinics vary by age group. In children, sex ratios of natal boys to girls range from 2:1 to 45:1. In adolescents, the sex ratio is close to parity; in adults, the sex ratio favors natal males, with ratios ranging from 1:1 to 61:1. In two coun- tries, the sex ratio appears to favor natal females (J apan: 2.2:1; Poland: 3.421).
Because expression of gender dysphoria varies with age, there are separate criteria sets for children versus adolescents and adults. Criteria for children are defined in a more con- crete, behavioral manner than those for adolescents and adults. Many of the core criteria boys and girls. Young children are less likely than older children, adolescents, and adults to express extreme and persistent anatomic dysphoria. In adolescents and adults, incon- gruence between experienced gender and somatic sex is a central feature of the diagnosis.
Factors related to distress and impairment also vary with age. A very young child may show signs of distress (e.g., intense crying) only when parents tell the child that he or she is “really" not a member of the other gender but only ”desires” to be. Distress may not be manifest in social environments supportive of the child’s desire to live in the role of the other gender and may emerge only if the desire is interfered with. In adolescents and adults, distress may manifest because of strong incongruence between experienced gender and somatic sex. Such distress may, however, be mitigated by supportive environments and knowledge that biomedical treatments exist to reduce incongruence. Impairment (e.g., school refusal, development of depression, anxiety, and substance abuse) may be a conse- quence of gender dysphoria.
Gender dysphoria without a disorder of sex development. For clinic-referred children, onset of cross-gender behaviors is usually between ages 2 and 4 years. This corresponds to the developmental time period in which most typically developing children begin ex- pressing gendered behaviors and interests. For some preschool-age children, both perva- sive cross-gender behaviors and the expressed desire to be the other gender may be present, or, more rarely, labeling oneself as a member of the other gender may occur. In some cases, the expressed desire to be the other gender appears later, usually at entry into elementary school. A small minority of children express discomfort with their sexual anat- omy or will state the desire to have a sexual anatomy corresponding to the experienced gender ("anatomic dysphoria”). Expressions of anatomic dysphoria become more com- mon as children with gender dysphoria approach and anticipate puberty.