Lady Gaga believes there is "a lot of shame" attached to mental illness.

Lady Gaga

Lady Gaga

The 31-year-old singer has opened up to Prince William about her personal battles with depression in a FaceTime chat, and the star has revealed she felt "very nervous" when she first started discussing her issues publicly because of the stigma surrounding the condition.

Speaking about her issues in a video chat as part of the prince's charity Heads Together campaign, which the 34-year-old royal is spearheading alongside his wife Duchess Catherine and his 32-year-old brother Prince Harry, the 'Million Reasons' hitmaker said: "It made me very nervous at first.

"For me, waking up every day and feeling sad and going on stage is something that is very hard to describe. There's a lot of shame attached to mental illness. You feel like something's wrong with you."

And although the Gaga has has acquired three Brit Awards, six Grammy Awards and a Golden Globe gong for her role in 'American Horror Story: Hotel', her mental illness left her feeling "sad" and "full of anxiety" because she couldn't appreciate the "wonderful things" she owned or the successes she had achieved.

She continued: "In my life, I go, 'Oh my goodness, look at all these beautiful, wonderful things that I have. I should be so happy,' but you can't help it it if, in the morning when you wake up, you are so tired, you are so sad, you are so full of anxiety and the shakes that you can barely think."

Gaga - whose full name is Stefani Germanotta - spoke about her struggle with post-traumatic stress disorder (PTSD) in an open letter for the first time in December last year, and she believes addressing her internal fight helped her to overcome her battles, and she has encouraged other people facing the same problem she did to speak about it.

She explained: "It was like saying, 'this is a part of me and that's OK.'

"Even though it was hard, it was the best thing that could come out of my mental illness was to share it with other people and let our generation as well as other generations know that if you are feeling not well in your mind, you are not alone.

"We have to make the strongest most relentless attempt we can to normalise mental health issues, so people feel they can come forward."