18. Demi Lovato
Looking at her strong vocal performance and all of her success in life, you would have never thought Demi Lovato had to check into rehab.
In the end of 2010, after her breakup earlier that year with her longtime boyfriend, Joe Jonas, Demi quit the Jonas Brothers tour.
Before that, she got into a cat-fight with one of her female backup dancers. However, she was not reported to have any addiction problems.
She checked into rehab to seek medical treatment for emotional and physical issues. Rumor has it, she tended to hurt herself physically and she had an eating disorder.
