Attention-Deficit/Hyperactivity Disorder (ADHD) is a condition characterized by an attention span that is less than expected for the age of the person; there is often also age-inappropriate hyperactivity and impulsive behavior. Some use the term ADD, (Attention Deficit Disorder), to refer to the predominantly inattentive type of ADHD, since that type does not feature hyperactive symptoms. Others use the terms ADD and ADHD interchangeably, but ADHD is the only “official” term for the disorder.

The most commonly diagnosed behavior disorder in young persons, ADHD affects an estimated 5%, or 6.1 million, of American children aged 2-17, an average of at least one child in every classroom. In general, boys with ADHD outnumber girls with the disorder by about three to one. The combined type of ADHD is the most common in elementary school-age boys, while the predominantly inattentive type is found more often in adolescent girls. The disorder is sometimes not diagnosed until adolescence or adulthood, and half the children with ADHD have symptoms of the disorder throughout their lives.

Nearly two-thirds (64%) also had another mental, emotional, or behavioral disorder, such as conduct disorder, anxiety, depression, autism, and Tourette syndrome.