In a recent survey of 250 families whose children developed symptoms of gender dysphoria during or right after puberty, Lisa Littman, a physician and professor of behavioral science at Brown University, found that over 80 percent of the youth in her sample were female at birth. Littman’s study reported many other surprising findings. To meet the diagnostic criteria for gender dysphoria, a child typically needs to have shown observable characteristics of the condition prior to puberty, such as “a strong rejection of typically feminine or masculine toys," or “a strong resistance to wearing typically feminine or masculine clothes." Again, 80 percent of the parents in the study reported observing none of these early signs in their children.

The plot thickens again: First, many of the youth in the survey had been directly exposed to one or more peers who had recently "come out" as trans. Next, 63.5 percent of the parents reported that in the time just before announcing they were trans, their child had exhibited a marked increase in Internet and social media consumption. Following popular YouTubers who discussed their transition thus emerged as a common factor in many of the cases. After the youth came out, an increase in distress, conflict with parents, and voiced antagonism toward heterosexual people and non-transgender people (known as “cis” or “cisgender”) was also frequently reported. This animosity was also described as extending to “males, white people, gay and lesbian (non-transgender) people.” The view adopted by trans youth, as summed up by one parent, seemed to be that:

“In general, cis-gendered people are considered evil and unsupportive, regardless of their actual views on the topic. To be heterosexual, comfortable with the gender you were assigned at birth, and non-minority places you in the ‘most evil’ of categories with this group of friends. Statement of opinions by the evil cis-gendered population are consider phobic and discriminatory and are generally discounted as unenlightened.”

Parents further reported being derogatorily called “breeders” by their children, or being routinely harassed by children who played “pronoun-police." The observation that they no longer recognized their child’s voice came up time and again in parental reports. In turn, the eerie similarity between the youth's discourse and trans-positive online content was repeatedly emphasized. Youth were described as “sounding scripted," “reading from a script,” “wooden,” “like a form letter,” “verbatim,” “word for word," or “practically copy and paste."

Littman raises cautions about encouraging young people’s desire to transition in all instances. From the cases reviewed in her study, she concluded that what she terms “rapid-onset gender dysphoria” (ROGD) appears to be a novel condition that emerges from cohort and contagion effects and novel social pressures. From this perspective, ROSD likely exhibits an aetiology and epidemiology that is distinct from the "classical" cases of gender dysphoria documented in the DSM.

https://www.psychologytoday.com/us/blog/culture-mind-and-brain/201811/why-is-transgender-identity-the-rise-among-teens