The Britain's Got Talent star, who has learning difficulties, told British newspaper the News of the World: 'When I was 17 I did think about doing something nasty. It was all psychological. I was damaged, I had to get help from a professional - I also had to see a doctor, who gave me treatment.'
But Boyle said it is not a sign of weakness to get help.
The 49 year-old said: 'You mustn't be afraid to do that, it's not a sign of weakness - it gave me the confidence to fight back, knock on people's doors, audition and finally get what I wanted.
'In my case it was a small group of teenage girls that put me in that place, they're the worst kind.'