Boyle was admitted to London's Priory Clinic on Sunday, a day after she finished behind a male dance group on the show "Britain's Got Talent," the Sun newspaper reported.
"Nobody has had to put up with the kind of attention Susan has had. Nobody could have predicted it," one of the show's judges, Piers Morgan, told breakfast TV show GMTV. "It has been crazy, she has gone from anonymity to being the most downloaded woman in history."
Boyle was favored to win the show's finals -- watched by more than 19 million people -- after a clip from her first appearance became the fifth most-watched in YouTube history, viewed more than 220 million times.