In Creativity is Forever, Gary Davis listed 22 characteristics that were most commonly found in creative people, some positive (curiosity, independent, risk-taking, high energy, emotional) and some negative (impulsive, hyperactive, argumentative).
He found that many of these traits were shared by those with ADHD, (Attention deficit hyperactivity disorder,) a common condition affecting as many as 3% of children and adolescents and continuing into adulthood for some.
Lacking a mental filter, difficulty in ignoring the imaginative side of the brain, and difficulty holding attention were strongly shared traits between those with ADHD and the highly creative.
So little surprise that ADHD diagnosed people are more likely to reach higher levels of creativity.
You can read more on the Scientific American Blog.