Duke and Duchess of Cambridge have encouraged people to keep talking about mental health in order to remove the stigma.
The royal couple appeared in a new video clip for the Time to Change campaign on Thursday, in which they thanked those who have "shared their experiences" in order to help other people but stressed there is still a need to "keep talking" and "keep taking action".
Prince William said: "We wanted to say a big thank you to everyone who has shared their experiences and taken action through Time To Change, helping to challenge the stigma which surrounds mental health.
"Over the past 15 years, Time To Change champions have inspired and supported thousands of people across the country, and mental health has now, at last, moved into the mainstream as part of our daily lives.
"We need to keep talking, keep taking action and continue to stand up to the stigma."
His wife, Duchess Catherine, added: "Movements like Time To Change have helped to transform attitudes and encourage more openness about mental health in schools, communities and the workplace.
"However, the work isn’t done yet and we cannot afford to stop here.
"It's so important that we value our mental health just as much as we value our physical health."
In February, the royal couple - who have three children together - highlighted the Time to Change initiative on their Instagram account.
They shared a short clip of "Can a small conversation make a difference?" being typed into a Google search bar and alongside the GIF, added the caption: "It's easy to think we haven't got the power to make a change. But a small conversation can make a big difference when it comes to tackling the stigma surrounding mental health. #TimeToTalk."