Susan Boyle has revealed she suffers from Asperger's Syndrome, a form of autism.
The singing sensation, who found fame after appearing on Britain's Got Talent in 2009, said it was a relief to finally receive a diagnosis after years of not knowing what made her "different".
She was misdiagnosed with brain damage when she was a child.
"I went to seek a diagnosis from a Scottish specialist," Boyle told the Observer. "Nobody told me to. I thought I had a more serious illness and couldn't function properly.
"[When I was a kid] I was told I had brain damage. I always knew it was an unfair label. Now I have a clearer understanding of what's wrong and I feel relieved and a bit more relaxed about myself."
She added: "I have always known that I have had an unfair label put upon me. That made me more determined to be where I want to be."
The specialist found that Boyle's IQ was above average.
"Asperger's doesn't define me," she said. "It's a condition that I have to live with and work through, but I feel more relaxed about myself. People will have a greater understanding of who I am and why I do the things I do."
Asperger's syndrome is characterised by significant difficulties in social interaction and nonverbal communication, alongside restricted and repetitive patterns of behaviour and interests.
People with the condition often suffer from anxiety, frustration and relationship difficulties due to their inability to communicate.
The Scottish mezzo-soprano, who has suffered from depression in the past, admits that it helps to be surrounded by a network of support.
"I am not strong on my own," she said. "When I have the support of people around me, I am fine."
Charities hailed Boyle's decision to go public with her condition as "inspiring".
National Autistic Society chief executive Mark Lever said Boyle had "played an important role in bringing the issue to the nation's attention".
He said: "Autism can have a profound and sometimes devastating effect on individuals and families but public understanding and support can make a huge difference."