Speaking to the Los Angeles Times about her friendship with the singer, Sia said:
She had a real breakdown.
She's on stage with 10 candied lollipops and clowns and dancers, selling the dream, the joy, the happiness — and that's really hard sometimes when you're not feeling it yourself.
Perry also opened up about the experience, explaining that the relatively lukewarm reception to her 2017 album Witness knocked her confidence.
I think the universe was like 'okay, all right, let's have some humble pie here. My negative thoughts were not great. They didn't want to plan for a future.
I also felt like I could control it by saying 'I'll have the last word if I hurt myself or do something stupid and I'll show you — but really, who was I showing?
Sia believes that Perry's emotions were an opportunity to reassess her relationship with music. She said:
I knew she was driven and ambitious, that was clear from the beginning. But I didn't realise that she was so reliant on that validation for her psychological wellbeing.
She did say 'I feel lost'. I think it was a big kick to her ego, but it was the best thing that could have ever happened to her, really, because now she can make music for the fun of it. Getting number ones does nothing for your inside.
The friendship between Perry and Sia began when Sia started to find fame and success as a singer in 2014. Perry acted like something of a mentor, inducting Sia into life in Hollywood.
Sia also talked to Perry and her now-fiancé Orlando Bloom separately during the couple's breakup — without the other knowing. Whether or not her advice contributed to their getting back together, the couple reunited in 2018 and Perry is now expecting her first child with the actor.
The process of repairing her relationship also helped her to recognise and care for her mental health, Perry explained.
Having distracted herself from negative thoughts with shopping, travelling and eating for years, when first began dating Bloom she "wasn't ready for the growth" he was interested in pursuing. But now she practices transcendental meditation and has taken part in the Hoffman Process, a retreat she described as providing "ten years of therapy condensed into a week".
Perry has opened up about her depression before. 2017 was a particularly dark period for the singer, as she explained to the LA Times.
I was kind of clinically depressed and I didn't know what my life was. I couldn't really even imagine living, to be completely honest.
Processing these emotions in the years that followed have led her to the production of her latest album, Smile. Songs like 'Never Really Over' and 'Champagne Problems' reflect how Perry is now in a better place, having survived her breakdown.
If you have been affected by any of the issues in this article, The Samaritans offers support; you can speak to someone for free over the phone, in confidence, on 116 123 (UK and ROI), email [email protected], or visit the Samaritans website to find details of your nearest branch.