Australian singer-songwriter Sia says her bipolar disorder is the result of smoking too much marijuana as a child.
In one of her most candid interviews yet, the reluctant pop star told American radio host Howard Stern she thinks her bipolar II diagnosis can be linked to smoking the drug at age 13.
"What I do think, is that I smoked too much pot as a kid," she said.
"My brain wasn't fully formed.
"I f***ed my brain up."
Sia, who refuses to show her face on stage, also opened up about how her father's dual personalities - the kind Phil and the anguished Stan - affected her childhood.
"When Stan came round, stuff got scary," she said.
But she stressed that he'd never been physically violent: "It was an energy that came in the room."
Sia always assumed her father suffered from dissociative identity disorder, although he's never been diagnosed or treated for it.
The hitmaker admitted her father, an "incredible" guitarist in his own right, could be envious of her success.
"I think it's impossible not to see something you wanted happen to someone else and maybe wish it for yourself," she said.
Laughing as she told the story, the Adelaide-born singer said she'd once offered to help her dad with his own album, only to be abruptly refused.
When Stern asked how that made her feel, she said it was "amusing" and she didn't take it personally.
Despite her sometimes difficult childhood, Sia says she enjoyed a good relationship with her parents and was still recovering from her alcohol addiction.
"I didn't know who I was until three-and-a-half years ago," she confessed.