At one time or another, we've all encountered a child whose challenging, sometimes bizarre behavior leaves us puzzling over what's going on in the young person's head.

Perhaps at the grocery store, we've watched a frustrated parent call an errant child's name repeatedly and implored him or her to "put that down" and "don't touch that" and "keep your hands to yourself." Maybe there was a child at school who couldn't seem to sit still and was in constant motion. Maybe the child appeared always to be daydreaming in class or couldn't focus on any task long enough to finish it. Perhaps, we tell ourselves, the child is bored or the task to easy, so it's natural the student wants to move on to something else.

Attention deficit hyperactivity disorder (ADHD) has many faces and remains one of the most talked-about and controversial topics in parenting and education. Hanging in the balance of heated debates over medication, diagnostic methods and treatment options are children, adolescents and adults who must each day manage the condition and lead productive lives. To help parents, caregivers, teachers, school administrators and others better understand this mental health condition, the U.S. Department of Education, with the assistance of its Office of Special Education and Rehabilitative Services and Office of Special Education Programs, have put together some vital information for everyone who interacts with a person diagnosed with or displaying symptoms of ADHD.

ADHD Defined and Described

This neurological condition involves problems with inattention and hyperactivity-impulsivity that are developmentally inconsistent with the age of the child. Research has increasingly shown that ADHD is not a disorder of attention; instead, it's a function of developmental failure in the brain circuitry that monitors inhibition and self-control. This loss of self-regulation impairs other important brain functions crucial for maintaining attention, including the ability to defer immediate rewards for later gain.

Children with ADHD can also exhibit excessive motor activity. The high energy level and subsequent behavior are often misperceived as purposeful noncompliance when, in fact, they may be a manifestation of the disorder that requires specific interventions.

What makes this condition so confounding is that children with ADHD can exhibit a range of symptoms and levels of severity. Additionally, many children with ADHD often are of average intelligence and have a range of personality characteristics and individual strengths.

The typically behavior associated with ADHD is classified into two main categories: poor sustained attention and hyperactivity-impulsiveness. As a result of the range of behaviors children with the condition can exhibit, three subtypes of the disorder appear in the fourth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders:

• ADHD predominantly inattentive (ADHD-PI or ADHD-I)
• ADHD predominantly hyperactive-impulsive (ADHD-PHI)
• ADHD combined (ADHD-C)

A child expressing hyperactivity commonly appears fidgety, has trouble staying seated or playing quietly and acts as if driven by a motor. Children displaying impulsivity often have difficulty participating in tasks that require taking turns. Other common behaviors of ADHD may include blurting out answers to questions instead of waiting to be called on and flitting from one task to another without finishing.

The inattention component of ADHD affects the educational experience of these children because ADHD makes it difficult for them to attend to detail in directions, sustain attention for the duration of a task and misplace needed items. These children often fail to give close attention to details, make careless mistakes and avoid or dislike tasks requiring sustained mental effort. Children with ADHD may also experience difficulty in reading, math and written communication. Although these behaviors are not in themselves a learning disability, almost one-third of all children with ADHD have learning disabilities, according to the National Institute of Mental Health.

Furthermore, ADHD commonly occurs with other conditions: Research suggests that approximately 40 to 60 percent of children with ADHD have at least one coexisting disability. Although any disability can coexist with this mental health condition, certain disabilities seem to be more common than others. In addition to learning disabilities, the more common condition coinciding with ADHD include disruptive behavior disorders, mood disorders, anxiety disorders and tics and Tourette's syndrome.

ADHD affects children differently at different ages. In some cases, children initially identified as having ADHD-PHI are subsequently identified as having ADHD-C as their attention problems surface.

The characteristics of this disorder affect not only children's academic lives but often their social lives as well. Children with ADHD-PHI may show aggressive behaviors, while children with ADHD-PI may be more withdrawn. Because they're less disruptive than children with ADHD who are hyperactive or impulsive, many children diagnosed with ADHD-PI go unrecognized and unassisted. Both types of children with ADHD may be less cooperative with other children and adults, and they may be less willing to wait their turn or play by the rules. Because they're unable to control their own behavior, they may experience social isolation. Consequently, their self-esteem may suffer.

In the U.S., an estimated 1.46 to 2.46 million children--that's 3 to 5 percent of the student population--have ADHD, per the American Psychiatric Association. Boys are four to nine times more likely to be diagnosed with the condition, and the disorder is found in all cultures, although prevalence figures differ.