She told Attitude magazine: "When I was really skinny, I wanted to kill myself. I was miserable, like inside and out, for four years of my life."

Citing pressure from music executives, she added: "But no-one cared, because aesthetically you make sense."

The American Idol winner added: "It was a very dark time for me. I thought the only way out was quitting."

She said the way she spent a lot of her time exercising during that period.

"I like wrecked my knees and my feet because all I would do is put in headphones and run. I was at the gym all the time."

The singer said that she turned things around after the release of third album My December in 2007, when she took creative control of her career by producing and co-writing the entire record, which had a darker, rockier sound.

"There's a song on My December called Sober. There's this line 'picked the weeds but kept the flowers' and I just live my life by that because you are who you surround yourself with," she told Attitude.

"I was around some really negative people, and I got out of it because I had a lot of great people there, too. It was a case of turning around, facing them and walking toward the light," she added.

"Not everybody has my personality and it doesn't bounce off everybody."