Unknown: Attention-Deficit Hyperactivity Disorder

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Unknown: Attention-Deficit Hyperactivity Disorder

Causes and Symptoms
The Future
For more information


Attention-deficit hyperactivity disorder, or ADHD, is a developmental disorder usually associated with children but increasingly recognized in adults too. People with ADHD are easily distracted, have trouble

focusing or paying attention, are disorganized, and frequently behave in impulsive ways.

The disorder has been known to doctors for over a century. The earliest description of it was written by a German doctor in 1845, about his own son. In 1902 a British doctor named George Still gave a series of lectures to other doctors, in which he described children who would now be called hyperactive and impulsive. Still thought that the disorder might be genetic in origin. He emphasized the fact that the behavioral problems in these children did not result from bad parenting.

There are three basic types of ADHD: inattentiveness; impulsiveness; and a combination of the two.


The central characteristic of all three types of ADHD is that the child (or adult) diagnosed with the disorder has fallen behind in school and in social relationships. Children diagnosed with the inattentive type of ADHD daydream in school; do not seem to listen when someone speaks directly to them; do not follow instructions and fail to complete chores or homework assignments; have trouble with tasks that require concentration; and are in general disorganized. They are more easily overlooked by parents and teachers, however, because their behavior is not as disruptive as the hyperactivity or impulsiveness of other children diagnosed with ADHD.

Children diagnosed with the hyperactive or impulsive type of ADHD are the ones who cannot sit still in school. They call out answers or talk all the time, get up and walk around the room, or try to do several things at once. They do not think before they speak, act without considering the consequences of their actions, or have trouble taking turns with other children. Teenagers with this type of ADHD may say that they feel inwardly restless much of the time or need to find things to do to keep busy.

One important thing to keep in mind about ADHD is that the behaviors—whether inattentiveness, hyperactivity, or a combination of both—must be inappropriate to the child's age and must continue for six months or longer. Not every episode of absentmindedness or fidgeting in school means that a child has ADHD. In addition, children's personalities differ, including their level of activity and their level of interest in certain activities. For example, some children have no difficulty finishing their homework in a subject that interests them but may have trouble focusing on an assignment in a subject they do not like.

The signs of ADHD in adults are often harder to recognize than in children. Adults with ADHD are more likely to say that they have trouble relaxing than feeling that they have to race around physically. Inattentiveness may take the form of forgetting meetings, work deadlines, or social get-togethers. Impulsiveness may take the form of moodiness, temper tantrums, or impatience in traffic jams.


According to the National Institute of Mental Health (NIMH), between 3 and 7 percent of children in the United States have ADHD. This group would include about 2 million children as of 2008. Worldwide, the rate of ADHD in children is thought to be somewhere between 8 and 12 percent.

Boys are three to five times more likely than girls to be diagnosed with ADHD. The inattentiveness subtype is more common in girls than in boys, however. As far as is known, ADHD is equally common in all racial and ethnic groups in the United States.

In adults, the gender ratio is virtually equal. The rate of ADHD in American adults is thought to be between 2 and 7 percent.

Causes and Symptoms

The causes of ADHD are not completely understood, but studies of brain function using positron emission tomography (PET) scans indicate that

the brains of children with ADHD may be structured differently from those of children without the disorder. More specifically, some researchers think that the parts of the brain that govern attentiveness do not have normal levels of dopamine, a chemical produced by the brain that allows nerve cells to transmit signals from one cell to another. The fact that medications that stimulate the release of dopamine are beneficial to children with ADHD supports this theory.

There are also genetic factors involved in ADHD even though no specific gene has been identified as a cause of the disorder. It is known that the disorder runs in families. The parents and siblings of children with ADHD are two to eight times more likely to develop ADHD than the general population.

Some researchers think that environmental toxins, particularly lead, and a mother's drinking or smoking during pregnancy are risk factors for ADHD in the child. There is also some evidence that very low birth weight or premature birth may be risk factors for ADHD. It is not known whether the emotional climate in the child's family contributes to the disorder, although some doctors think that mood or anxiety disorders in other family members may make the child's symptoms worse. Other unproven theories include the idea that ADHD is caused by head injuries, allergic reactions to food additives, or a diet high in sugary foods.

Symptoms of inattentiveness related to ADHD include:

  • Failing to pay close attention to details; frequently making careless mistakes.
  • Having difficulty paying attention to tasks for more than a few minutes.
  • Appearing not to listen when spoken to.
  • Not following through on instructions and failing to complete homework or other tasks.
  • Having difficulty organizing tasks.
  • Frequently losing pencils, books, or other items necessary to complete homework or other tasks.
  • Being forgetful.
  • Being easily distracted.

Symptoms of impulsiveness and hyperactivity include:

  • Fidgets or squirms in seat.
  • Leaves classroom seat and runs around.
  • Has difficulty playing quietly.
  • Seems to be constantly on the go.
  • Talks a lot; finds it hard to keep quiet.
  • Blurts out answers in class.
  • Finds it hard to take turns or wait in line.
  • Butts in on conversations or intrudes on the privacy of others.


The diagnosis of ADHD is complicated, not only because the child's age, overall personality, and medical history must be taken into account, but also because about 45 percent of children with ADHD have at least one other psychiatric disorder, most commonly anxiety disorders, depression, Tourette syndrome, or bipolar disorder. There is no single laboratory test, imaging study, or neurological test that can be used to diagnose ADHD, although there are behavioral checklists and questionnaires that doctors can use to narrow the diagnostic possibilities. The diagnosis usually follows a series of interviews with psychiatrists and psychologists as well as the child's pediatrician. A complete physical examination is important to rule out vision problems, hearing loss, seizure disorder, or hyperthyroidism as possible causes of the child's behavior.

The diagnosis of ADHD in children is based on whether the child meets the criteria specified in a diagnostic manual on mental disorders:

  • The symptoms must have started before the child was seven years old.
  • The child must have had the symptoms over a period of at least six months.
  • The child must have six or more of the signs or symptoms of inattentiveness or hyperactivity/impulsiveness listed in the previous section.
  • The symptoms must be shown to have affected the child's ability to function in at least two areas of life, usually home, relationships with friends, and schoolwork. Thus, a child who is impulsive or inattentive at school but relates well to friends or other family members would not be diagnosed with ADHD.

A set of criteria called the Wender Utah Rating Scale is commonly used to diagnose ADHD in adults:

  • A history of ADHD in childhood
  • Hyperactivity and poor ability to focus or concentrate
  • Difficulty completing tasks
  • Mood swings
  • Difficulty controlling temper
  • Inability to handle stress
  • Impulsive behaviors


Treatment for ADHD usually includes a combination of medications and behavior therapy. The use of medications has been controversial. However, children treated with both medications and behavior therapy have been found to do better than those treated with behavior therapy alone. It is important to understand that the medications prescribed for ADHD do not cure the disorder. The medications only help the child control the symptoms, and they must be taken every day.

The medications most commonly used to treat ADHD are psychostimulants, which work by targeting the parts of the brain that produce dopamine. These drugs include Ritalin, Adderall, and Dexedrine. More recently, the Food and Drug Administration (FDA) approved the use of a non-stimulant medication called Strattera, which works on another brain chemical called norepinephrine. Norepinephrine is a hormone that affects a person's ability to pay attention and respond appropriately to stress. Although medications for ADHD generally work well, they do have side effects, such as sleep problems, weight loss, appetite loss, and nervousness.

In addition to behavior therapy, children with ADHD may receive social skills training and attend support groups. Many doctors recommend parenting skills training for the parents of children with ADHD and family therapy for the entire family.

Adults with ADHD are also treated with a combination of drugs and psychotherapy. However, because adults need larger doses of psychostimulants than children do, they must see their doctor periodically to make sure that the drugs are not interfering with other medications they may be taking, particularly drugs to control high blood pressure.

Some forms of alternative medicine that have been suggested as treatments for ADHD include special diets, vitamin supplements, and various herbal preparations. There is no evidence, however, that any of these alternative approaches are useful for children or adults with the disorder.


Doctors think that between 30 and 70 percent of children diagnosed with ADHD will continue to have some symptoms of the disorder as adults. Most children diagnosed with the disorder benefit from appropriate treatment, although they have a higher risk of alcohol and drug abuse in adolescence. As many as 65 percent may continue to have problematic symptoms of ADHD that keep them from reaching their full academic or work potential in adult life.


There is no known way to prevent ADHD because the causes of the disorder are still not completely understood.

The Future

Doctors are not certain whether the rate of ADHD in the American population is likely to increase or remain at its present level. Current research on the disorder includes studies comparing newer drugs for ADHD to older psychostimulants; studies of ADHD in adults; studies of the relationship of childhood ADHD to substance abuse in adolescence and adulthood; and evaluations of new diagnostic questionnaires for ADHD.

SEE ALSO Bipolar disorder; Lead poisoning; Prematurity; Seizure disorder; Tourette syndrome


Dopamine: A brain chemical that helps to regulate movement.

Norepinephrine: Another brain chemical that affects a person's ability to pay attention.

Psychostimulant: A type of drug that increases the activity of the parts of the brain that produce dopamine.

For more information


Brynie, Faith Hickman. ADHD: Attention-Deficit/Hyperactivity Disorder. Minneapolis, MN: Twenty-First Century Books, 2008.

Peirce, Jeremy. Attention-Deficit/Hyperactivity Disorder. New York: Chelsea

House, 2008.

Silverstein, Alvin, Virginia Silverstein, and Laura Silverstein Nunn. The ADHD Update: Understanding Attention-Deficit/Hyperactivity Disorder. Berkeley Heights, NJ: Enslow Publishers, 2008.


Baruchin, Aliyah. “Attention Deficits That May Linger Well Past Childhood.” New York Times, January 10, 2008. Available online at http://health.nytimes.com/ref/health/healthguide/esn-adhd-ess.html (accessed September 3, 2008).

“Patient Voices: ADHD.” New York Times, May 21, 2008. Available online at http://www.nytimes.com/interactive/2008/05/21/health/healthguide/TE_ADHD_CLIPS.html (accessed September 3, 2008). This is an interactive site with voice recordings and slide shows of nine children and adults coping with ADHD.


Children and Adults with Attention-Deficit/Hyperactivity Disorder (CHADD). Understanding AD/HD. Available online at http://www.chadd.org/AM/Template.cfm?Section=Understanding (accessed September 4, 2008).

KidsHealth. What Is Hyperactivity? Available online at http://kidshealth.org/kid/health_problems/learning_problem/adhdkid.html (updated May 2006; accessed September 3, 2008).

Mayo Clinic. Attention-Deficit Hyperactivity Disorder (ADHD). Available online at http://www.mayoclinic.com/health/adhd/DS00275 (updated February 16, 2007; accessed September 3, 2008).

National Alliance on Mental Illness (NAMI). Attention-Deficit/Hyperactivity Disorder. Available online at http://www.nami.org/Template.cfm?Section=By_Illness&template=/ContentManagement/ContentDisplay.cfm&ContentID=22571 (updated May 2003; accessed September 3, 2008).

National Institute of Mental Health (NIMH). Attention Deficit Hyperactivity Disorder (ADHD). Available online at http://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtml (updated April 3, 2008; accessed September 3, 2008).