ADHD is characterized by a persistent and dysfunctional pattern of overactivity, impulsiveness, inattention, and distractibility.

Etiology
The disorder runs in families and cosegregates with mood disorders, substance use disorders, learning disorders, and antisocial personality disorder.

Families with a child diagnosed with ADHD are more likely than those without ADHD offspring to have family members with the above-mentioned disorders.

The etiology of the disorder is unknown, but perinatal injury, malnutrition, and substance exposure have all been implicated. Many children with ADHD have abnormalities of sleep architecture (decreased rapid eye movement latency, increased delta latency), EEG, and soft neurologic signs.

Epidemiology
The prevalence of ADHD in school-age children is estimated to be 3% to 5%. The boy-girl ratio ranges from 4: 1 in the general population to 9: 1 in clinical settings. Boys are much more likely than girls to be brought to medical attention.

Clinical Manifestations
History, Mental Status Examination, and Laboratory Tests
To meet criteria for ADHD, a child must evidence the onset of inattentive or hyperactive symptoms before age 7; symptoms must also be present in two or more settings (e.g., school, home). Symptoms in only one setting suggest an environmental or psychodynamic cause.

Preschool-age children are usually brought for evaluation when they are unmanageable at home.

Typically, they stay up late, wake up early, and spend most of their waking hours in various hyperactive and impulsive activities. Children with a great deal of hyperactivity may literally run about the house, cause damage, and wreak havoc.

When these children enter school, their difficulties with attention become more obvious. They appear to not follow directions, forget important school supplies, fail to complete homework or inclass assignments, and attempt to blurt out answers to teachers’ questions before being called on. As a result of their inattention and hyperactivity, these children often become known as “troublemakers.”
They fall behind their peers academically and socially.

Evaluation of the child involves gathering a careful history from parents and teachers (the latter usually through report cards and written reports). The child’s behavior with and without the parent is carefully observed during psychiatric assessment. Informal testing is carried out by having the child attempt to complete a simple puzzle, write the letters of the alphabet, distinguish right from left, and recognize letters traced on the palms (graphesthesia).

Physical examination, particularly focusing on neurologic function, is imperative. No specific laboratory or cognitive tests are helpful in making the diagnosis.

Differential Diagnosis
It is important to distinguish symptoms of ADHD from age-appropriate behaviors in active children (running about, being noisy, etc.). Children can also appear inattentive if they have a low or a high IQ and the environment is overstimulating or understimulating, respectively. In either instance, IQ testing and careful evaluation of the school program will clarify the diagnosis.

Children with oppositional defiant disorder may resist work or school tasks because of an unwillingness to comply with others’ demands but not out of difficulty in attention.

Children with other mental disorders (e.g., mood disorder, anxiety disorder) can exhibit inattention but typically not before age 7. The child’s history of school adjustment is not usually characterized by teacher or parent reports of inattentive, disruptive behavior.

Symptoms that resemble ADHD can occur in children before age 7, but the etiology is typically a side effect of a medication (e.g., bronchodilators) or a psychotic or pervasive developmental disorder; these children are not considered to have ADHD.
Of course, ADHD may be comorbid with any of the above disorders. A dual diagnosis is made only when it is needed to explain the full clinical picture.

Management
The management of ADHD involves a combination of somatic and behavioral treatments. Most children with ADHD respond favorably to psychostimulants.

Methylphenidate is the first-line agent, followed by D-amphetamine. Clinicians try to use the smallest effective dose and to restrict use to periods of greatest need (i.e., the school day) because psychostimulants have undesirable long-term physical effects (weight loss and inhibited body growth). Some children can be treated effectively with agents that raise norepinephrine in the brain, such as bupropion (Wellbutrin) or atomoxetine (Strattera) a norepinephrine reuptake inhibitor.

Behavioral management techniques include positive reinforcement, firm limit setting, and techniques for reducing stimulation (e.g., one playmate at a time; short, focused tasks).