Story highlights Princes William and Harry and the Duchess of Cambridge talk about mental health in a video released Friday

Addressing his mother's death, William said "it's very easy to run away from it"

The conversation was part of the Heads Together campaign, which aims to end the stigma around mental health

(CNN) It is rare for the Duchess of Cambridge, wife of Prince William, to speak candidly on film. But in a video released Friday, Kate talks openly with her husband and Prince Harry about mental health and the importance of discussing mental wellbeing.

The video, filmed at Kensington Palace earlier this week, is part of the Heads Together campaign , which aims to end the stigma around mental health. The three young royals have been spearheading the campaign since its launch in 2016.

In the film, Kate talks openly about the struggles she has faced as a mother.

"Having a child, particularly your first child, is such a life-changing moment. Nothing can really prepare you for that," she explained.

Turning to her husband with a wry smile, she said, "Remember the first few days with little George? You have no idea what you're doing."