"There's a lot of shame attached to mental illness, you feel like something's wrong with you".
In the conversation, they emphasized how there shouldn't be a stigma when it comes to talking about mental illness.
In an interview with the Daily Telegraph, Harry revealed he spent almost 20 years "not thinking" about his mother's death and eventually got help after two years of "total chaos".
Prince William has said the "shock" of his mother's death is still with him, 20 years after she was killed in a auto crash in Paris.
In December, Gaga opened up in a letter about her own battles with PTSD after she was sexually assaulted at 19 years old.
The clip, in support of the Duke of Cambridge's Heads Together campaign which he leads alongside Kate Middleton and Prince Harry, features the unlikely pair sharing a FaceTime call from their respective homes in Los Angeles and London. "We have to make the strongest, most relentless attempt we can to normalise mental health issues, so that people feel like they can come forward", she added.
"It made me very nervous at first".
They have been intensifying their campaign in the run up to the London Marathon, and hoping the thousands of runners who will be pounding the streets of London on Sunday will be wearing their blue Heads Together headbands. For me, waking up every day and feeling sad and going on stage is something that is very hard to describe. "I should be so happy.' But you can't help it if in the morning, when you wake up, you're so exhausted, you're so sad". "But, it was like saying this is a part of me, and that's okay". You won't be judged. "I still feel, 20 years later about my mother, I still have shock within me". We're starting to talk... For him, it is very important to "break open that fear, that taboo", and that being open about it is the best start in addressing mental illnesses.
"When you've heard so many stories from so many other people and if you can relate to that then it's only right that you talk about your own experiences".