Matt Short / Barcroft Media via Getty Images Paddy McGuire, a 10-year-old transgender girl, is pictured in her home in Leicester, England in 2017.

There's been a lot of discussion in the last year about how parents should respond when children say they're transgender. According to a new study, the answer might be to trust them — even if they're as young as three.

The study, conducted by psychologists including Kristin Olson, who runs University of Washington's TransYouth Project, looked at the interests and behaviour of over 250 children, aged 3 to 12, over about 3 and a half years.

The research found that what could be considered gender-based interests and identities children hold are unlikely to change with age.

The study, which also included psychologists from from Oxford University and the University of Massachusetts Amherst, split kids up into three groups. There were the children who had "socially transitioned" (that is, had changed their gender pronouns, the gendered way they dress or wear their hair, and their name); children who conformed to the gender they had at birth; and children who were gender-nonconforming in some way. The kids in the third group all had some degree of interest in toys, clothing or behaviour usually associated with the opposite sex than the one they were assigned at birth.

Peter Cade via Getty Images A new study has found that the more young children's interests differ from their birth gender, the more likely they are transition.

After reconnecting with the gender nonconforming kids two years after initially asking them about their gender identity, the study found that the stronger a child's gender nonconformity, the more likely they were to socially transition. So a girl who preferred playing with trucks but otherwise was interested in largely "feminine" behaviour was less likely to transition than someone who was born a girl but told researchers they felt more like a boy, preferred to play with boys, dressed more like a boy, and also preferred trucks.

In other words, it was the children's self-described gender behaviour and identity that determined if they transitioned later on. Other factors, such as their parents' political affiliation or income, had little effect.

"I think this wouldn't surprise parents of trans kids, and my findings are often 'duh' findings for them," Olson told The Atlantic. "It seems pretty intuitive."

Charlotte Tate, a psychologist at San Francisco State University and herself a trans woman, told the magazine that the study reiterates something she's found in many conversations with trans people.

"One of the most consistent themes is that at some early point, sometimes as early as age three to five, there's this feeling that the individual is part of another gender group," she said. When told that they're part of their assigned gender, "they'll say, 'No, that's not right. That doesn't fit me.' They have self-knowledge that's private and that they're trying to communicate."

The study also made another significant discovery about gender identity in kids. Whether or not they make the transition to living as another gender does little to change their identity and preferences, researchers found. So a transgender girl who is still living as a boy feels just "as female" as after making the transition. This seems to indicate that forcing trans kids to live as their birth identity won't actually "stop" them from identifying as another gender.

Researchers also say that a trans girl's pre- and post-transition female identity is "comparable in degree" to that of a cisgender girl, who was born female and identifies that way.

The study does have some limitations. For example, the researchers write that their sample size is small, and there isn't a huge amount of diversity in terms of income, education or race. Transgender children are an area that could benefit from more study, the psychologists say.

Olson told CBS News that it's common for trans children to experience gender dysphoria, a "persistent unhappiness, discomfort, and distress about the incongruence between the gender that you are assigned, based on your anatomy at birth, versus the way you internally experience gender."

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