SINEAD O'Connor has officially joined the U.S. mainstream, thanks to her well-received appearance on Oprah last week. Why would an internationally beloved icon like Oprah Winfrey seek the company of the highly controversial Sinead? Oprah was doing a show on the devastating effects of bipolar disorder, and as Sinead has admitted to having the disease she turned out to be the perfect guest.

The timing of last Thursday's appearance also couldn't have been better, as Sinead released her new CD Theology earlier this year, and she'll soon embark on a U.S. tour. The ladies chatted thoughtfully about bipolar, and the despair it's brought to Sinead's life.

"It's like being a bucket with holes in it. Just leaking tears from every pore," Sinead told Oprah about her frequent episodes of waking up crying for no apparent reason.

"It's almost very difficult to explain when you are the person that suffers from the thing, but the best way I can describe it is it's almost like before you get ill, you are a solid wall," she added. "And while you're ill, it's like the bricks are falling away and it's one teetering little brick."

Sinead looked healthy and was the model of composure during her appearance. She sported her trademark crew, which seems to be speckled with a bit of grey these days now that she's hit the big 4-0, and looked comfortably casual in t-shirt and jeans - no Posh-like makeover for her, we're happy to report.

She spoke of the abuse she suffered as a child in her household, and how it made her anxious and unable to experience any kind of joy. Depression sank in when she hit her twenties, and her rising fame didn't help. Three years ago she was finally diagnosed as bipolar, and has been taking medication ever since.

Not that she wanted to at first. "But I said, 'I've got nothing to lose,'" and, she says, she took them for the first time.

"It was brilliant because I felt this huge hole. And when I took the meds, within half an hour, it was literally like I felt concrete coming in to fill the hole.

"Everything just became too much, and the best way I can describe it to you is you're so sad, just terribly sad, that you're like a bucket of water with holes in it. Every pore of you is crying and you don't even understand why or what," she added. "I actually kind of died and got born again as a result of taking the meds and having a chance to, you know, build a life."

Well, good for her. Sinead also admits that her four children have been a rock of support.

"I'd be a headless chicken without the kids, yeah, definitely," she says. "They create a routine."

The conversation on the show eventually turned to that other troubled star making daily headlines, Britney Spears. Sinead is fully on her side.

"I feel very sorry for her. She's only a young girl. She's had two babies in the space of two years and (doesn't seem to be getting) a terrible amount of support from the people around her. We all have issues; no-one's perfect," Sinead says.

"I think it's terrible what the media are doing to her here. I'd invite her to come and live in Ireland, to escape. I feel so sorry for celebrities in this country. It's absolutely impossible to live a normal life."