It’s been a year and a half since Julia Michaels’ inescapable breakout hit “Issues” peaked at No. 11 on the Hot 100. Since then, the singer has scored Grammy noms for best new artist and song of the year and appeared on tracks alongside the likes of Shawn Mendes, Keith Urban, Maroon 5 and Rita Ora.

Now, Michaels is following up her debut mini-album, 2017's Nervous System, with Inner Monologue Part I, a six-track project that includes two new duets with Selena Gomez and Niall Horan. Though Michaels has worked with both previously -- she co-wrote several tracks on Gomez's 2015 Revival LP and opened for Horan on the U.K. leg of his world tour -- their new team-ups mark the first time they’ve shared the mic together.

Below, Billboard tells Michaels about how her new collabs came together, her upcoming tour with Pink and why she's using her platform to talk about mental health: “I'm happy that I have the outlet to talk about it and help people not feel so alone in the way that they feel.”

Why did you call this project Inner Monologue?

I decided to call it Inner Monologue because these are things that I think and feel on a daily basis. I'm either talking to myself or I'm talking to somebody else. So it's like my deepest thoughts and feelings that I just want to let out into the universe and not keep inside.

Why did you break this project into two parts?

I'm going on a lot of tours this year, and I want to just have a new one for each tour. I also don't want to give all of me too soon, you know?

Stars like Lady Gaga and Demi Lovato, as well as your collaborator and friend Selena Gomez, have been very vocal about mental health in recent years. On your new song “Anxiety,” and throughout the project, you sing about your own experiences. Do you think it's an important topic?

One hundred percent. I think there's still a lot of people that feel like they are not allowed to [feel that way], or they suppress it because they think it's a taboo thing to talk about. This generation is just becoming way more emotionally evolved, and it's something that we should talk about.

You and Selena have worked together a lot in the past, but this is your first proper duet. Why was “Anxiety” the right track?

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." 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. Or a female empowerment thing. 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 okay with it.”

Your other new duet is with Niall Horan on the song "What a Time." You've toured together in the past -- what’s he like in the studio?

To be honest, he’s kind of the same. He walks in, and he's just his goofy, silly self. 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.

And speaking of tours, in a few months you're hitting the road with Pink, which is a pairing I am so excited for.

Oh, you have no idea. I'm so excited to watch her do all those crazy, beautiful acrobatics.

You wrote with her on her latest album, Beautiful Trauma. What is your relationship with her like?

Oh my goodness, she's amazing. I had a meeting with an artist prior to meeting her, and it was one of those things where it was really weird. And I was like really nervous to meet Alecia [Pink's real name], because she's somebody that I look up to: What if this goes horribly? But I walked in, and she was just such an open book, so kind and such a badass. She doesn't take shit from anybody. She spills her whole heart on the table, and I just I love that. I can relate to that, because I do the same thing. I'm so excited that I get to do this tour and be around such a strong, beautiful woman. This is my first tour with a woman; I've only toured with guys up until now. I'm really, really excited.

There's one lyric on Inner Monologue Part I that really stood out to me: “Sometimes I think I kill relationships for art/ I start up all this shit to watch them fall apart/ I pay my bills with it,” from “Happy.” Is that true?

[Laughs] Yeah. I have this tattoo that says, “art aint easy.” I feel like a lot of creative people do this thing where you feel like you do a lot of things to be inspired. Sometimes you'll pick fights with somebody in order to write about it. Or you'll do something you wouldn't normally do just to feel inspired. I've definitely been the kind of person to do things like that in the past, just for some exciting lyrical content. I'm not proud of it, but it's definitely something I've done.

How will Inner Monologue Part II differ from this one?

I think it will probably stay in the same realm. I just usually write about things that I know, and a majority of things that I know are relationship-based. I talk about connections and intimacy and love and heartbreak, because those are the things that I know best. And to me, all of those things -- whether they're painful or they're beautiful -- that is poetry to me. I was going originally do sort of all heartbreak songs and then the second part would be all love songs. But now I'm just all over the fucking map.