Sia says fame makes her feel "crazy."

The 39-year-old singer, who is known for disguising her face at public events with her signature blonde wig, explained: "It literally f**ks with my sanity. I stop feeling authentic because I'm trying to find ways to say the same thing differently. And after a while, you can't. It becomes bad for my self-esteem.

"People say, 'Enough of this s**t where she doesn't show her face'...I'm trying to do this differently, for serenity. And it's a fun game for me as well. I have nothing to lose. But of course I want to be loved. So when people say, 'Show your face, you're not ugly.' I want to say, 'I know. I'm not doing it because I think I'm ugly; I'm trying to have some control over my image. And I'm allowed to maintain some modicum of privacy. But also I would like not to be picked apart or for people to observe when I put on ten pounds or take off ten pounds or I have a hair extension out of place or my fake tan is botched. Most people don't have to be under that pressure, and I'd like to be one of them."

In "only the fourth interview" she has ever done with pal Kristen Wiig for Interview magazine, Sia also claims she originally wanted to give away her album '1000 Forms of Fear' for free.

She explained: "I had no plans to promote it or tour it. I was newly sober and I didn't want to be a famous singer. So I delivered it to the label in the U.K...But we weren't sure what would happen if I wasn't willing to show my face and do promo and go on tour and do the traditional kind of pop strategy. So I had no expectations. Because of that, I was able to take a great risk, which is the risk of failure as a solo artist, because I was already gratefully making good money writing pop songs for pop stars."