Former champion boxer Frank Bruno has told a Sunday newspaper that he used cocaine for six months, plunging him into a "black hole with no ending".
Cocaine use was damaging to his mental health, Bruno says
He said the drug, which he first took in 2000, may have contributed to the mental illness for which in 2003 he was sectioned under the Mental Health Act.
"Cocaine took control of my brain. I wish I'd never seen the stuff," the 43-year-old told the News of the World.
Bruno won the WBC world heavyweight title at Wembley Stadium in 1995.
A year later he lost his title to Mike Tyson and was then forced into retirement by an eye injury.
He was divorced from wife Laura, the mother of his three children, in 2001.
An interview with Bruno and extracts from his autobiography are published in the News of the World.
He said he first took cocaine after being given some by fellow English visitors to Las Vegas, where he had watched a fight.
"It was like nothing I'd ever taken before. I did it again. And again. It was nice - too nice," he said.
But he added: "It's a horrible, very, very false world that it puts you under. I felt great when actually things weren't so great.
"I loved the buzz it gave me but I couldn't stand coming down."
Bruno told the paper: "Taking it was the worst thing I could have done in my mental condition - it was like a black hole with no ending."
Cocaine "scared" him and he "had to walk away" after just six months, he said.
He soon afterwards tried high-strength "skunk" cannabis, as "a way to escape".
"Down as I was, I knew it was a dumb move. I stopped almost as soon as I started. But stopping didn't make me feel any better," he said.
In 2003, Bruno received psychiatric treatment at Goodmayes Hospital in Ilford, Essex, after being detained under the Mental Health Act at his home near Brentwood.
Bruno also admitted using cannabis to "calm himself down" after fights, having first tried the drug at the age of 12.
But he added: "Coke makes you feel weird, nasty, edgy, gangstery, fighty, just crazy
"Using drugs is not a nice experience. I'm talking about it now because I think it's better that I come clean."
Bruno lifted the WBC boxing title when he outpointed Oliver McCall in September 1995.
At the height of his fame, he was one of Britain's most popular sportsmen, also making regular TV appearances and starring in panto.