In Touch Weekly seems to think so:

The warning signs were there – but few knew the extent of Britney Spears‘ anguish, until now. Days before Britney was rushed to the hospital on January 4, she left a suicide note, In Touch has exclusively learned. According to the insider, the troubled pop star, left it on her bathroom counter, where it was allegedly found by Sam Lutfi. “The letter was very said,” says a friend. “It was filled with reasons why she shouldn’t live, included lines from poems about death. She said in it she was sorry for never making her life what everyone else wanted. She mentioned how lonely and unfair life could be, how peaceful death seems and how your mind would finally be at ease.” The friend adds, “She went on and on about wanting to just rest in peace.”