Dr. Goepferd, of Children’s Hospital Minnesota, pointed to another possible reason for the smaller proportion of older transgender people: Because of lower access to health care, along with high rates of H.I.V., violence and suicide, transgender people are more likely to die at younger ages.

Dr. Hammack described a person he interviewed who talked about how difficult it was to come out as nonbinary in their fifties because “we look around, and everybody’s so young.” And others who identified as masculine or butch lesbians, he said, have told him, “If I was that young, maybe I would have gone down that path, but it wasn’t available.”

Mx. Giles said they realized they were nonbinary after finding a community of like-minded people on Tumblr.

“It signifies a new confidence among a new generation to be authentic in their gender identity,” said Phillip Hammack, a professor of psychology and director of the Sexual and Gender Diversity Lab at the University of California, Santa Cruz.

“That’s the bewildering question of why this is all happening,” Dr. Herman said.

“There is no one who knows how many trans people or how many gay people or bisexual people died of suicide this past year,” said Amit Paley, head of The Trevor Project, a suicide prevention group that recently released its own report based on social media polling, showing that young L.G.B.T.Q. people had high rates of mental health issues and suicidal thoughts.Adve

only 47 percent

The study found people 13 to 25 accounted for a disproportionately largely share of the transgender population. While younger teenagers were just 7.6 percent of the total U.S. population, they made up roughly 18 percent of transgender people. Likewise, 18- to 24-year-olds made up 11 percent of the total population but 24 percent of the transgender population.

Although the total estimated number of transgender people was small — around 1.6 million people 13 and up, or about 0.6 percent of the population — trans identification in recent years has become political dynamite, driven in part by the rise in minors seeking medical treatments. Republican legislators across the country have sought to prohibit such care by criminalizing doctors or investigating parents for abuse, which professional medical groups have condemned.

But nearly one-quarter of the adults in the surveys who said they were transgender identified as “gender nonconforming.”

The notion of what it means to live as a transgender person is also shifting. Dr. Goepferd, who is nonbinary, noted that many teenagers would not necessarily want or need hormones or surgeries to transition to another gender, as was typical of older generations.

Experts said that young people increasingly have the language and social acceptance to explore their gender identities, whereas older adults may feel more constrained. But the numbers, which vary widely from state to state, also raise questions about the role of peer influence or the political climate of the community.

1.3 percent of 18- to 24-year-olds were transgender, compared with about 0.5 percent of all adults.

The laws proposed – and in some cases passed – were written to have a direct effect on transgender people’s ability to access physical and mental health care.

But, for many of her patients, physical interventions – including puberty blockers, hormone treatments or surgery – are the best way they can align their physical bodies with their gender identity. For transgender people seeking care who haven’t started puberty or are still in its early stages, puberty blockers are often an initial treatment. As Coles explains, “These medications work like a pause button on the physical changes caused by puberty. They are well studied, safe and completely reversible.”

“Blocking people from accessing gender-affirming care creates increased risks for social isolation, suicide ideation and depression,” writes shuster. But they also explain that “little scientific evidence exists to support the use of current trans medical treatments, therapy or decision-making that meets evidence-based standards.”

The key phrase there is “evidence-based standards.” One of the reasons for this lack of evidence that care works is pretty simple, according to shuster. “Randomized controlled trials have been implausible, given that only 0.6% of the population identifies as trans or nonbinary.” This isn’t to say that doctors are flying blind. As Mandy Coles explains, there is a good and ever-growing amount of evidence gathered in other ways to support many types of interventions. But compared with other medical interventions, guidance is murky, says shuster. As they put it: “How might someone who is trained to manage illness and disease ‘treat’ someone’s gender identity, which is neither an illness nor a disease?”

This lack of clear clinical guidelines is compounded by a lack of training. A study in 2016 found that most medical providers only get one day of training on transgender issues. All this adds up to medical providers feeling a lot of uncertainty in the care they give, shuster found in their research.

Puckett sees a similar trend in how fast people made transitions. “Gen Z and millennials also reported much shorter gaps between reaching milestones. For instance, the boomers group reported an average 24-year delay between starting to identify as trans and living in their affirmed gender. There was just a two- and three-year gap for Gen Z and millennials, respectively.”

Puckett wrote a story for The Conversation that explains that younger generations are more diverse in gender than older generations. Nearly a quarter of Gen Z participants “identified as nonbinary, whereas only 7.4% of boomers identified this way,” Puckett writes. Another interesting generational difference is the age at which people began to pass through the milestones of coming out. On average, people in every generation realized they “felt different” at around 10 to 13 years old. But “boomers reported reaching the other major milestones later than younger groups,” Puckett explains. “For example, boomers were, on average, around age 50 when they were living in their affirmed gender all the time. In contrast, Gen X was 34, millennials were 22 and Gen Z was 17.”