Selena Gomez jumped at the chance to work with singer pal Julia Michaels on her new anxiety-related tune, because she wanted to bring awareness to the issue.

Gomez, Lady Gaga and Demi Lovato have opened up about their mental health battles and Selena felt Julia had really nailed the issues in the lyrics to her new song Anxiety, and when Michaels asked her to duet on the track, she didn't hesitate.

"When I sent it to her, I was like, 'Hey, what do you think about this?' and she was like, 'This is amazing. I want to do it'," Michaels tells Billboard.

"And I think this was the song that works the best for us, because it's something we both struggle with. It's something we've always talked about. It's something that's very relatable to both of us.

"We also liked the idea of doing a song together, where we're talking about our relationship with anxiety. We're not talking about our relationship with men or us fighting over somebody or something like that - those things that are typical duets for women... This is a female empowerment thing, but it’s completely different. We're not throwing our fists in the air, but we're saying, 'Hey, we have anxiety, but we're OK with it'."

Julia also recruited One Direction star Niall Horan for another duet on her new album, insisting he's very easy to work with.

"He walks in, and he's just his goofy, silly self," she explains. "I can't think of a moment where him and I aren't laughing and being completely ridiculous with each other. We always make fun of each other for a second, then he sings his heart out, and then he's like, 'Cool, I'll see you later'. And all of a sudden there's this magical vocal on this song, and he sounds like a sweet baby angel."