Despite diagnoses for attention-deficit/hyperactivity disorder (ADHD) occurring in a reported 11 percent of U.S. school-aged kids, clinicians still don't fully understand the underlying causes of this common condition. Now a brain marker may be on the horizon, thanks to a new approach that provides evidence of a relationship between brain structure and dimensional measures of ADHD symptoms. The study's results are reported in an Article in Press in Biological Psychiatry.