In the 1970s, attention deficit hyperactivity disorder (ADHD) was considered a childhood disorder that went away in adolescence or early adulthood. It later became clear that the symptoms persist in some adults, changing the way we think about the disorder.

Source: http://qz.com/687248/new-research-shows-some-adults-who-never-had-adhd-as-kids-are-developing-it-now/