Duchess Kate takes over Huffington Post UK as guest editor for a day

Duchess Kate of Cambridge, who wears hats and tiaras so well, put on a new cap Wednesday: She's guest editor of the Huffington Post UK for the day.

It may be the first time a British royal has been a guest editor but it's for one of Kate's good causes: She's trying to give more of her spotlight to improving children's mental-health policies, to dispel the taboo of talking about it in public and to help parents and kids find resources they need.

Thus, the royal hashtag: #YoungMindsMatter, and the launching of Kate's new global initiative.

"The mental health of our children must be seen as every bit as important as their physical health," she wrote in her first blog essay for the site. "For too long we have been embarrassed to admit when our children need emotional or psychiatric help, worried that the stigma associated with these problems would be detrimental to their futures. "

She said research published today by the Huffington Post UK shows that a third of parents worry that they will look like a bad parent if their child has a mental health problem.

"Parenting is hard enough without letting prejudices stop us from asking for the help we need for ourselves and our children," she wrote.

Kensington Palace sent out a stream of tweets promoting content on the website.

First lady Michelle Obama also wrote an article for the site, endorsing Kate's campaign and praising her for shining "a bright light on mental health, particularly children's mental health, and on the tens of millions of people who suffer in silence."

The British outpost of Arianna Huffington's massive and massively successful news-and-liberal-opinion website set up a temporary editorial office in Kensington Palace for the day so Kate can be close to her London home, the sprawling Apartment 1A in the palace.

Kate was deemed editor-chic by the blogs that track her fashion, wearing a Reiss high-neck white blouse and a tweedy herringbone-pattern black boucle wool skirt by Dolce & Gabbana over black tights and suede pumps.

For Kate, 34, who has only rarely spoken in public and has never done an in-depth interview, this is the first time she has worked so closely with a media organization.

But she's calling the shots. As patron to several charities associated with the issue, Kate commissioned articles, blogs and videos from leading experts on child mental health to raise awareness about exploring kids' psychological well-being without fear or embarrassment.

Get her rewrite! Duchess Kate will 'guest edit' HuffPost UK

She'll be discussing the content with writers and reporters and will help plan when the material is released on the site throughout the day.

"The Duchess will use the opportunity to highlight the inspiring work being done by parents, teachers, researchers, and mental health professionals around the country," Kensington Palace said in a statement when it announced the plan last month.

Kate wrote that shortly after her 2011 marriage to Prince William, she took up patronage of charities dealing with children and addiction and family breakdown, and heard many "heartbreaking" stories. (She announced today she is adding another patronage, the Anna Freud Center, a children's mental-health charity in London where she has visited several times.)

"It was...clear that with mental health problems still being such a taboo, many adults are often too afraid to ask for help for the children in their care," she wrote. "It is time for this to change."

She wrote that she and William wouldn't hesitate to seek help if Prince George or Princess Charlotte need it in the future (Charlotte is still a baby, George is a toddler who will turn 3 this year).

"We hope to encourage George and Charlotte to speak about their feelings," she wrote. "We know there is no shame in a young child struggling with their emotions or suffering from a mental illness."

She urged people to read the content on the site. "Together, we have the chance to make a real difference for an entire generation of young children."

Huff Post UK commissioned a poll of British parents that found nearly a quarter worry that their children are facing mental health issues.

"The research reveals that there has never been a more important time to talk about mental health with young people," said the site's editor-in-chief, Stephen Hull. Last month he said in a statement that mental-health issues has been a major editorial focus for the site.