SEATTLE — Meghan Trainer’s second child was born a boy, but at age 4½, Brody became Brie and now lives as a girl.

For the Federal Way mother of four, there was never a question about supporting and accepting her transgender daughter, who turns 6 on Saturday.

“I was putting her to bed one night and she said: ‘Mommy, why did God make me a boy? I’m really a girl,’ ” Trainer, 39, recalled. “I told her God doesn’t make mistakes. I promised her that her dad and I would help her be her true self.”

It turns out that probably was the best approach, according to a new study by University of Washington researchers published Friday in the journal Pediatrics.

In a first-ever look at mental health among transgender children, Kristina Olson, a UW assistant professor of psychology, found that such kids with family support had normal levels of depression and anxiety — similar to typical children.

The results challenge long-held assumptions that transgender kids are destined to have psychological problems, said Olson, who runs the TransYouth Project at UW.

And they run counter to grim results of previous research, which shows far higher rates of depression, anxiety and suicide in transgender youth and adults than in the general population.

“I didn’t expect them to be doing quite this well,” Olson said.

Instead, the study of 73 transgender kids ages 3 to 12 found no higher rates of depression than in two control groups, including their own siblings and non-transgender children in the community. Rates of anxiety were slightly higher than the national norm, but not enough to raise concern.

The study, which recruited kids in the U.S. and Canada, included only children who had “socially transitioned,” that is, who were living openly as the opposite gender. And it included only children who were aided in the transition by their families.

The findings are significant because they provide the first data-based guidance for parents of transgender children who often are not sure what to do, said Dr. Johanna Olson, medical director of the Center for Transyouth Health and Development at Children’s Hospital Los Angeles.

“I think this is a wonderful, wonderful piece of work,” said Johanna Olson, who was not involved in the UW study and isn’t related to Kristina Olson.

It backs up what clinicians, parents and support groups have known for years, she said, “which is that kids who are supported in their authentic gender do very well.”

For Meghan Trainer and her husband, Ryan Trainer, 40, a registered nurse, the path was clear. Brie’s change didn’t happen overnight. Rather, it followed years of the child’s interest in all things female.

“She always loved pink and wore dresses and found things to make girl hair,” Meghan Trainer said. “Her draw was always to My Little Pony. And dress-up was huge for her, and she was always the girl.”

For the couple, also parents to two sons, Chaz, 7, and Maddox, 4, and a daughter, Kennedi, 2, allowing Brie to change her name, her dress and her pronouns just made sense.

“Our philosophy is that you need to love and support your child no matter what,” Trainer said.

It’s significant that Brie exhibited a key factor in children who have what’s called “gender dysphoria,” in which a person’s emotional and sexual identity is the opposite of the gender at birth.

That’s different from kids who simply like toys or clothes associated with the opposite sex, or who may simply wish they were a different gender, Kristina Olson said.

“The criterion is consistent, insistent, persistent,” Olson said. “There are a very small subset of gender-nonconforming kids who believe themselves the opposite of the gender assumed at birth.”

Limited statistics estimate that transgender adults make up between 0.3 percent and 1 percent of the population, a figure that may apply to children as well, Olson said.

Many people ask how children as young as 3 can possibly decide they’re a different gender, Olson said. But science shows that nearly all children understand their gender identity surprisingly early.

“It’s kind of an unfair question,” she said. “Why should we believe any other kid knows their gender if these kids aren’t allowed to know theirs?”

So far, Brie’s change has gone smoothly, Meghan Trainer said. Their kids are home-schooled, so bullying isn’t the issue it might have been. This week, everyone went to Great Wolf Lodge in Thurston County, like any other family.

But Trainer admits she’s anxious about the future. They’ve already consulted with endocrinologists about so-called “puberty blockers” that halt the hormones of adolescence.

“I hear that we are in this little golden time frame now,” she said. “Puberty makes me a little nervous.”