AP 'X Factor' judges Simon Cowell and Britney Spears attend the FOX network upfront presentation party at Wollman Rink, Monday, May 14, 2012 in New York. Photo: Evan Agostini Britney Spears suffers from Attention Deficit Hyperactivity Disorder (ADHD). The 'Hold it Against Me' singer has walked off set on a number of occasions while judging auditions on her first of 'The X Factor' in the US, and a source says this is because she can't take medication for her disorder. The source told RadarOnline: "Britney was diagnosed with ADHD in her teens and used to take medication for it. "The medication helped her deal with it, however, she can't take it now because it interferes with the other medications she takes for her mental health issues. "Britney's current team of doctors strictly prohibit her from taking Adderall or Ritalin, which are commonly given to people with ADHD." Show head Simon Cowell - who appears alongs...