Diseases & Conditions


Attention Deficit/Hyperactivity Disorder (ADD, ADHD)

Attention deficit/hyperactivity disorder (ADHD) is poor or short attention span and impulsiveness inappropriate for the child's age; some children also manifest hyperactivity.

Although there is considerable controversy about incidence, it is estimated that ADHD affects 5 to 10% of school-aged children and is diagnosed 10 times more often in boys than in girls. Many features of ADHD are often noticed before age 4 and invariably before age 7, but they may not interfere significantly with academic performance and social functioning until the middle school years. ADHD was previously just called "attention deficit disorder"; however, the common occurrence of hyperactivity in affected children—which is really a physical extension of attention deficit—led to a change in the current terminology.

ADHD can be inherited. Recent research indicates that the disorder is caused by abnormalities in neurotransmitters (substances that transmit nerve impulses within the brain). The symptoms of ADHD range from mild to severe and can become exaggerated or become a problem in certain environments, such as in the child's home or at school. The constraints of school and organized lifestyles make ADHD a problem, whereas in prior generations, the symptoms may not have interfered significantly with children's functioning because such restraints were often much fewer. Although some of the symptoms of ADHD also occur in children without ADHD, they are more frequent and severe in children with ADHD.


ADHD is primarily a problem with sustained attention, concentration, and task persistence (ability to finish a task). The child may also be overactive and impulsive. Many preschool children are anxious, have problems communicating and interacting, and behave poorly. They seem inattentive. They may fidget and squirm. They may be impatient and answer out of turn. During later childhood, such children may move their legs restlessly, move and fidget their hands, talk impulsively, forget easily, and they may be disorganized. They are generally not aggressive.

About 20% of children with ADHD have learning disabilities and about 80% have academic problems. Work may be messy, with careless mistakes and an absence of considered thought. Affected children often behave as if their mind is elsewhere and they are not listening. They often do not follow through on requests or complete schoolwork, chores, or other duties. There may be frequent shifts from one incomplete task to another.

About 40% of affected children may have issues with self-esteem, depression, anxiety, or opposition to authority by the time they reach adolescence. About 60% of young children have such problems as temper tantrums, and most older children have a low tolerance for frustration.

Signs of ADHD

All signs do not have to be present for a diagnosis of attention deficit/hyperactivity disorder (ADHD). However, signs of inattention must always be present for a diagnosis. Signs must be present in two or more situations (for example, home and school) and must interfere with social or academic functioning. Signs of inattention: Often fails to pay close attention to details Has difficulty sustaining attention in work and play Does not seem to listen when spoken to directly Often does not follow through on instructions and fails to finish tasks Often has difficulty organizing tasks and activities Often avoids, dislikes, or is reluctant to engage in tasks that require sustained mental effort Often loses things Is easily distracted by extraneous stimuli Is often forgetful Signs of hyperactivity: Often fidgets with hands or feet or squirms Often leaves seat in classroom and elsewhere Often runs about or climbs excessively Has difficulty playing or engaging in leisure activities quietly Is often on the go or acts as if “driven by a motor” Often talks excessively Signs of impulsivity: Often blurts out answers before questions have been completed Often has difficulty awaiting his turn Often interrupts or intrudes on others


The diagnosis is based on the number, frequency, and severity of symptoms. Symptoms must be present in at least two separate environments (typically, home and school)—occurrence of symptoms just at home or just at school and nowhere else does not qualify as ADHD. Often, diagnosis is difficult because it depends on the judgment of the observer. There is no laboratory test for ADHD. Questionnaires about various aspects of behavior can help the doctor make the diagnosis. Because learning disabilities are common, many children receive psychologic testing both to help determine if ADHD exists and to detect the presence of specific learning disabilities.

ADHD: Epidemic or Over-Diagnosis?

An increasing number of children are diagnosed with attention deficit/hyperactivity disorder (ADHD). However, there is a growing concern among doctors and parents that many children are misdiagnosed. A high activity level may be completely normal and be simply an exaggeration of normal childhood temperament. Alternatively, it may have a variety of causes, including emotional disorders or abnormalities of brain function, such as ADHD.

Generally, 2-year-olds are active and seldom stay still. A high activity and noise level is common up until age 4. In these age groups, such behavior is normal. Active behavior can cause conflicts between parents and child and may worry parents. It also can create problems for others who supervise such children, including teachers.

Determining whether a child's activity level is abnormally high should not simply depend on how tolerant the annoyed person is. However, some children are clearly more active than average. If the high activity level is combined with short attention span and impulsivity, it may be defined as hyperactivity and considered part of ADHD.

Scolding and punishing children whose high activity level is within normal limits usually backfires, increasing the child's activity level. Avoiding situations in which the child has to sit still for a long time or finding a teacher skilled in coping with such children may help. If simple measures do not help, a medical or psychologic evaluation may be useful to rule out an underlying disorder such as ADHD.

Treatment and Prognosis

To minimize the effects of ADHD, structures, routines, a school intervention plan, and modified parenting techniques are often needed. Some children who are not aggressive and who come from a stable and supportive home environment may benefit from drug treatment alone. Behavior therapy conducted by a child psychologist is sometimes combined with drug treatment. Psychostimulant drugs are the most effective drug treatment.

Methylphenidate Some Trade Names RITALIN CONCERTA METHYLIN is the psychostimulant drug most often prescribed. It is as effective as other psychostimulants (such as dextroamphetamine Some Trade Names DEXADRINE ) and is probably safer. A number of slow-release (longer-acting) forms of methylphenidate Some Trade Names RITALIN CONCERTA METHYLIN are available in addition to the regular form and allow for one time per day dosing. Side effects of methylphenidate Some Trade Names RITALIN CONCERTA METHYLIN include sleep disturbances, such as insomnia, appetite suppression, depression or sadness, headaches, stomachaches, and high blood pressure. All of these side effects disappear if the drug is discontinued; however, most children have no side effects except perhaps a decreased appetite. However, if taken in large doses for a long time, methylphenidate Some Trade Names RITALIN CONCERTA METHYLIN can occasionally slow the child's growth; therefore, doctors monitor weight gain.

A number of other drugs can be used to treat inattentiveness and behavioral symptoms. These include clonidine Some Trade Names CATAPRES , amphetamine Some Trade Names ADDERAL -based drugs, antidepressants, and antianxiety drugs. Sometimes, combinations of drugs are used.

Children with ADHD generally do not outgrow their inattentiveness, although those with hyperactivity tend to become somewhat less impulsive and hyperactive with age. However, most adolescents and adults learn to adapt to their inattentiveness. Other problems that emerge or persist in adolescence and adulthood include poor academic achievement, low self-esteem, anxiety, depression, and difficulty in learning appropriate social behaviors. Importantly, the vast majority of children with ADHD become productive adults, and people who have ADHD seem to adjust better to work than to school situations. However, if the disorder is untreated in childhood, the risk of alcohol or substance abuse or suicide may increase.

Last full review/revision February 2003

Source: The Merck Manual Home Edition