MSNBC.com: Typical toddler behavior or ADHD? Ten ways to tell

Telling the difference between a normal, antsy 4-year-old and one who is hyperactive to the point where it affects his or her ability to learn has become trickier as attention deficit disorders have become more common, according to recent research. Attention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed mental health disorder among kids in preschool, and it is now found in one of every 11 school-age children. But 40 percent of all 4-year-olds have trouble paying attention. So for parents, realizing which behaviors are a sign of the disorder is of paramount importance for receiving the correct diagnosis and treatment, experts say. Read more and learn the signs.