Tyson Fury took cocaine to deal with depression brought on by not getting the recognition he felt he deserved after becoming world heavyweight champion, his trainer said.
Fury tested positive for the drug earlier this month after twice postponing a scheduled rematch against Wladimir Klitschko.
In a subsequent interview with Rolling Stone the troubled boxer revealed his struggles with mental illness, telling the magazine if "I could take my own life, and I wasn't a Christian, I'd take it in a second."
Peter Fury, the 28-year-old's trainer and uncle, told BBC Radio 5 Live's Sportsweek that he didn't believe the British boxer was addicted to drugs.
He said: "Whatever he's taken will be a result of the depression. The way he's been received since he won the world title, to him, in his mind, he wasn't recognised in anywhere near the way he should have been.
"It's a combination of all of this that put him into depression.
He went on: "He just wants some space totally away from boxing, which is understandable."
Fury defeated Klitschko for the WBA and WBO titles 11 months ago. But despite his successes his career has been mired by controversy including accusations of homophobia after outbursts from the star. Meanwhile, last month he pulled out of a rematch with Klitschko after being deemed "medically unfit".
The British Boxing Board of Control is meeting on Wednesday to discuss withdrawing his licence.
In a wideranging interview with Rolling Stone Fury talked about the personal issues, including his drug use and suicidal thoughts.
"I'm a manic depressive. I just hope someone kills me before I kill myself," he told the magazine. "I am seeking help but they can't do nothing for me ... I've been pushed to the brink. I can't take no more. I'm in a hospital at the moment. I'm seeing psychiatrists. They say I've got a version of bipolar. I'm a manic depressive. All from what they've done to me. All this s**t through boxing, through taking titles, through writing me off."
Peter Fury told the BBC he was uncertain what to believe in the interview and claimed some parts of it were incorrect.
"He said in his interview that he hadn't been training at all, he hadn't done any training for five months, well that's totally untrue."
Fury had been training at his boxing gym in Bolton, Lancashire and at a local members' sports club, his uncle said. Although he said the boxer was like "an empty shell" during training.