The singer was suffering “horrific” post-traumatic stress disorder at the time of his brief appearance last year before he dramatically walked out.
At the time of his abrupt departure he blamed “personal reasons” but rumours circulated of a bust up with professional partner Karen Clifton or row with head judge Len Goodman.
But he has now laid bare the true scale of his PTSD, saying he has forked out £500,000 on mental health treatment over the course of his life.
Will Young has revealed he considered breaking his legs as an excuse to withdraw from Strictly
Mr Young, 38, believes the distressing condition was triggered by separation as a newborn from his twin brother, Rupert, who was ill at birth and placed in an incubator.
It was so bad I thought – I’m not joking – I thought about breaking my leg
In an interview for mental health champion Bryony Gordon’s Mad World podcast he said: “Now, with twins, they’ll wrap them up together, but then they didn’t.
"It was pretty heavy. We came to life together and then [my brother] got pneumonia and was very ill.”
He said the problem magnified during unhappy years spent at a “vicious” prep school. It then flared up during his brief stay on Strictly when he developed a stammer and became fearful of walking out on stage.
Will Young was diagnosed with the PTSD while appearing in a West End production of Cabaret in 2002
He said: “I was really ill. I was dragging myself to rehearsals. I just couldn’t do it any more. It was so bad I thought – I’m not joking – I thought about breaking my leg.
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The Leave Right Now singer shot to stardom in 2002 winning the inaugural Pop Idol contest.
He was diagnosed with the PTSD while appearing in a West End production of Cabaret the same year.
On the cost of treatment, which has included three stays in a clinic, he said: “It’s really expensive. I’ve probably spent at least half a million quid.”
Will Young has laid bare the scale of his PTSD, saying he has paid £500K on mental health treatment Will Young quits Strictly Come Dancing Fri, October 14, 2016
Will Young sensationally quit Strictly Come Dancing yesterday due to 'personal reasons' but he's since insisted that he's 'absolutely dandy'.
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Before the 2016 series started the Berkshire-born openly gay performer, who has won two Brit awards and sold more than 8 million albums, said: “As a fan of Strictly for years, I have always imagined myself on the show, but the timing has not been right until now.
"Strictly is a show with fantastic live music and has an ethos of positivity and growth.
"I practice these two things every day and I will try my hardest to be the best dancer possible.”