Kevin Federline's bombshell-filled memoir about his marriage to Britney Spears did not cause the pop star to spiral out of control, a source exclusively tells Us Weekly, contrary to a recent report. "Kevin's book wasn't the catalyst for this," the insider says of Spears' arrest for driving under the influence. "It did upset her deeply and definitely didn't help matters, but her issues predate the book." Us Weekly has reached out to Spears' rep for comment.