ADHD, also called attention-deficit disorder, is a behavior disorder usually first diagnosed in childhood. It's characterized by inattention, impulsivity, and, in some cases, hyperactivity. There are three major types of ADHD: Combined type: This is the most common type of ADHD, characterized by impulsive and hyperactive behaviors as well as inattention and distractibility. Impulsive/hyperactive type: This is the least common type of ADHD, characterized by impulsive and hyperactive behaviors without inattention and distractibility. Inattentive and distractible type: This type of ADHD is characterized mainly by inattention and distractibility without hyperactivity. ADHD is one of the most researched areas in child and adolescent mental health, but its precise cause is still unknown. Evidence suggests that ADHD is a genetic, brain-based biological disorder. Low levels of the brain chemical dopamine are found in children with ADHD. Brain imaging studies using PET scanners show that brain metabolism in children with ADHD is lower in the areas of the brain that control attention, social judgment, and movement. Many parents of children with ADHD experienced symptoms of ADHD when they were younger, and ADHD is commonly found in brothers and sisters within the same family. Estimates suggest that about 2 million children (3 to 5 percent) have ADHD. Boys are two to three times more likely to have ADHD than girls. The symptoms of hyperactivity, when present, are almost always apparent by the age of 7 and may be apparent in very young preschoolers. Inattention or attention-deficit may not be evident until a child begins elementary school. You may be thinking, "Hey, all kids are hyperactive to some degree!" It's true, most symptoms seen in children with ADHD also occur in children without this disorder. However, in children with ADHD, these symptoms occur more frequently and interfere with learning, school adjustment, and, sometimes, with the child's relationships with others. The symptoms of ADHD may resemble other medical conditions or behavior problems, so a diagnosis is essential. A pediatrician, child psychiatrist, or qualified mental health professional usually identifies ADHD in children. A detailed history of the child's behavior from parents and teachers, observations of the child's behavior, and psychoeducational testing are needed. Further, because ADHD is a group of symptoms, often diagnosis depends on several types of evaluations, including physical, neurological, and psychological. The major components of treatment for children with ADHD include parental support and education in behavioral training, appropriate school placement, and medication (psychostimulants). Treatment with a psychostimulant is highly effective in most children with ADHD. These medications are used to balance chemicals in the brain that prohibit the child from paying attention and controlling impulses. Antidepressant medications also may help improve attention while decreasing aggression, anxiety, and/or depression. Parenting children with ADHD can be challenging. Classes in behavior management skills for parents can help reduce stress for all family members. These skills may include the use of "time out" or point systems, which can improve behaviors such as completing school work or keeping the child's hands to himself or herself. Preventive measures for ADHD aren't known at this time. However, early detection and intervention can reduce the severity of symptoms, improve the child's school performance, enhance the child's normal developmental process, and improve quality of life overall.