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Prince William said that every celebrity he had asked to support his Heads Together mental health initiative three years ago had refused.
The Duke of Cambridge told the World Economic Forum in Davos that "many" stars had been approached, but none wanted to be associated with a mental illness.
He also said that the war generation may have helped to create some of the stigma.
People preferred not to talk about such "horrible" events, a stoic attitude conveyed to their children.
The prince created Heads Together, launched to fight the stigma of mental health, in 2017 with the Duchess of Cambridge and Prince Harry.
Duke spoke to his audience of business leaders about his own mental health issues, explaining that there was a traumatic incident that he did not think he'd ever manage to recover".
He added that if he had not shown himself open to his colleagues about the situation, he would have "slipped on a slippery slope" mentally.
Visibly moved, he always found that the incident was "very difficult to talk about" because he was "very closely related to my children", George, Charlotte and Louis.
The prince has already spoken of "very traumatic" calls involving children while they were working for the air ambulance.
But he said that such feelings were "only human," adding, "Yes, you wear armor … but someday, something comes up that is closely related to your personal life. and who really takes you on a line. "
The issue of mental health is a major theme in Davos this year, with several sessions on the subject.
Studies show that one in four people will suffer from a mental illness at some point in their lifebut many people are still too embarrassed to admit that they have a problem.
Despite greater willingness to discuss the issue, the prince said that there was still a lot of stigma, which means "so many people are suffering in silence".
He added: "For some reason, people are embarrassed by their emotions – the British in particular," he told a large audience in Davos.
He feels that the British stiff upper lip, common to previous generations, has a lot to do with it.
This attitude was passed on to children, especially after the First and Second World Wars, when it became difficult to speak of "such horrible circumstances".
"A whole inherited generation [this way of coping]. This is how you manage your problems: you do not talk about it. "
But he said "that a new generation knows that this is not normal" and realizes that it's best to be open about what they're feeling.
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Prince William was at the Round Table with New Zealand Premier Jacinda Ardern
The prince urged companies to do more. "It should be so much easier to go to HR and talk about it, it has to come from the top."
Spot the signs
During the debate, participants were asked if they or someone they knew had suffered from a mental illness. Almost everyone in the room raised their hand.
The Duke of Cambridge attended the forum with New Zealand Premier Jacinda Ardern, who made tackling mental health issues a priority for her government.
She said it was a sad fact that everyone in New Zealand, a small country of less than 5 million inhabitants, knows of the existence of "someone who has Is a suicide ".
HSBC boss John Flint, also a panel member, said that in the "notoriously competitive" banking sector, mental health problems were common.
He said it was imperative that line managers talk about it to allow the lower-most members of the organization to open it.
"We are all sitting on the spectrum [of mental health]. I know there is a profound difference between when I feel best and when I am not, "he added.
Flint said the bank is training managers to detect signs of mental health problems so they can help staff manage them.
He said that makes sense commercially given the impact of the problems on worker performance.