With her shaved head and edgy songs, Grammy-winning singer Sinéad O'Connor was an unmistakable pop star in the late '80s and early '90s. She was notoriously rebellious, most famously causing controversy when she ripped up a photo of Pope John Paul II during a 1992 performance on Saturday Night Live. A few days later, a crowd at Madison Square Garden booed her off the stage. The incident played out for months in the media, and for years afterward, she was a tabloid target with London and Irish papers following her every move.

Now a 40-year-old mother of four, Sinéad says even as she was being hailed at age 23 as one of the most influential figures of her generation, she was suffering. Her legendarily erratic behavior stemmed from a terror-filled childhood and an undiagnosed bipolar disorder. "I was watching the previous show you did about bipolar disorder and you had that lovely woman—[Jenifer Lewis] on—and I really identified with her about this thing of when you close the dressing room door after the show, your whole other mind-set would kick in."