For parents of children who have it — and more than 1 in 10 do, per the CDC — ADHD is a behavioral scourge, making their kids impatient, restless, impulsive and easily bored. For adults who have it — an estimated 4.4 percent — the disorder can make it difficult to concentrate on one thing for any period of time. — Caitlin Dewey, washingtonpost.com