INTRODUCTION
Attention deficit hyperactivity disorder (AD/HD) is a condition typically first evident in early childhood. Symptoms include deficits in attention, concentration, and short-term memory. Behaviorally, children with AD/HD are overly active (as if “driven by a motor”) and unable to remain seated, highly distractible, and impulsive. Concerns about AD/HD often initially arise during kindergarten or first grade, since these deficits significantly impair academic performance and are disruptive in a typical classroom. However, AD/HD is increasingly viewed as a lifelong condition with functional impairment extending throughout adulthood.
Recent data suggest a 6–8% prevalence rate. To date, the majority of epidemiologic studies have been conducted in North America and Europe. However, available data suggest that the condition has similar prevalence rates in Asia, Africa, and Latin America with a pooled worldwide rate of 5.3%. However, there is also considerable variability in prevalence rates that may reflect differing diagnostic practices, differing definitions of the condition, or both. A recent US study by the Centers for Disease Control reported state-based prevalence rates ranging from 5.6% (Nevada) to 15.6% (North Carolina). AD/HD disproportionately affects males with a sex ratio between 3:1 and 9:1, with more conservative figures in clinic rather than community samples. Lower socioeconomic status (SES) has been associated with increased AD/HD rates in international studies.
There are two essential clusters of AD/HD symptoms: inattention and hyperactivity/impulsivity. Symptoms of AD/HD include either inattention (failing to give attention to detail, problems maintaining attention, not appearing to listen when spoken to directly, failure to follow through on instructions and to complete schoolwork or other tasks, problems with organization, avoiding activities requiring sustained concentration, losing important items, being easily distracted, and forgetfulness), or hyperactivity/impulsivity (fidgeting, inability to remain seated, inappropriate running and climbing, difficulty playing quietly, acting as if “driven by a motor,” excessive talking, blurting out answers before questions are finished, difficulty taking turns, and intruding upon others’ activities and/or conversations), or of both clusters. Children must have at least six symptoms from either (or both) the inattention group of criteria and the hyperactivity and impulsivity criteria, whereas older adolescents and adults (over the age of 17 years) must present with five. Most symptoms should have been present before the age of 12 years.
CASE ILLUSTRATION 1: PRESCHOOL CHILD
Four-and-a-half year old Ronnie has been dismissed from three preschools during the past 9 months. Ronnie’s mother brings a teacher’s note chronicling Ronnie’s recent behavior:
2/25 = “Ran out of classroom and was on his way out of the building before I stopped him.”
2/28 = “Threw all of the students’ coats on the floor . . won’t listen when he’s told to hang them up.”
3/2 = “Would not sit through story time. Threw milk cartons during lunch time.”
In your examination room, Ronnie is lying across your stool face down yelling, “I’m flying,” while pushing off from the walls with his feet. His mother, appearing exhausted, makes a few half-hearted attempts to get Ronnie to settle down but quickly gives up saying, “You see doctor, this is what it’s like.”
Although there are no precise longitudinal figures, AD/HD is increasingly accepted as a lifelong condition for many, if not most, patients. Development, however, does affect the symptom picture. Research indicates that at around the age of 9 years, hyperactivity and impulsivity begin to become less pronounced, whereas inattention and other cognitive deficits persist, with hyperactivity being replaced by restlessness and fidgeting.
With children referred in preschool or the early grades, there is typically a high level of parental distress and urgency. Hyperactivity may take the form of an inability to remain seated for more than 5 minutes at school or during family meals. Even when seated, the child may be swinging their legs, rocking, or picking up nearby objects. By the time they reach first grade, children may also have a number of scars on their legs, arms, and head, and can provide a number of stories about jumping off the garage roof, rear-ending a car with their bicycle, and running into countless pieces of furniture. Among older adolescents and adults, household chores may be initiated but not completed, bills are forgotten, sitting through a movie or presentation is extremely difficult, and others complain about the patient’s frequent conversational interruptions. The phrase “as if driven by a motor” captures the quality of the child’s activity level. Although the child, with adult urging, may sit relatively still for 2–3 minutes, they will begin moving around as if they cannot stop themselves. The hyperactive/impulsive behavior is not experienced as under the patient’s control—particularly among younger children.
CASE ILLUSTRATION 2: EARLY ELEMENTARY SCHOOL CHILD
Christopher is a 7-year-old boy and first grader, who is accompanied by both parents. They bring several notes that the teacher has sent to them since school began several months ago. They also bring samples of Christopher’s schoolwork. The teacher’s notes describe situations in which Chris got up from his seat to sharpen his pencil 20 times in the course of a day, was repeatedly told to stop playing with the girl’s hair who sits in front of him, and continued to yell out answers to the teacher’s questions before she finished speaking. Christopher’s parents say that he is not learning to read or spell because he is easily distracted and cannot follow the lessons. At home, they describe mealtime as a “hit and run” experience where Chris eats while alternately sitting and standing at the table for no more than 10 minutes, during which he frequently knocks over his milk. Christopher’s mother says she no longer takes him shopping because he runs off from her in the store and she is afraid he will get lost.
Impaired attention and concentration, distractibility, and short-term memory deficits are often misattributed to “laziness,” poor motivation, or “not caring” rather than a central nervous system disorder. Parents frequently complain about having to tell their child “a hundred times” to do something before the request “seems to register.” Multistep directions are particularly challenging for those of all ages with AD/HD. A mother tells her teenaged son to go upstairs and get his new pants to be hemmed, the sewing kit, and a piece of chalk. Fifteen minutes later, when he has not appeared, his mother goes upstairs to find him. He is in his room, trying on a shirt with his new pants in his hand, having forgotten what he was asked to do.
CASE ILLUSTRATION 3: MIDDLE ELEMENTARY SCHOOL CHILD
Miranda, a 9-year-old fourth grader, is seen because of poor grades. Her teacher describes Miranda as “spacey” with difficulty concentrating, paying attention, and remembering. However, she and Miranda’s mother both describe Miranda as a “sweet, sensitive, and helpful girl” without any disruptive behavior. A Vanderbilt Scale confirms this picture. The teacher’s version includes a comment that Miranda may have to repeat the grade unless her academic performance improves.
At school, inattention and poor concentration impair academic performance. Much of school success is still based on memorization. To encode material into longer-term memory for a test, it is necessary to pay attention to relevant information, relate it to existing knowledge, and rehearse in short-term memory. When this process is disrupted, retaining information from textbooks and classroom presentations is extremely challenging. In elementary school, a typical didactic process is that the teacher will present a lesson (e.g., steps involved in long division, identifying adverbs) with several examples of the concept and then students will individually work on exercises applying that particular concept. In the later elementary years through college, there is much greater emphasis on reading and retaining what is read. College students with untreated AD/HD often report that despite rereading material multiple times, they cannot remember it.
CASE ILLUSTRATION 4: ADOLESCENT
Josh, a 15-year-old, is brought in by his father for a drug test. Yesterday, Josh was suspended from school after a baggie of marijuana was found in his locker. He readily admitted smoking it several times a week for the past 6 months to “help calm me down.” Josh was diagnosed with AD/HD-mixed type at the age of 7 years and responded well to stimulant pharmacotherapy until about a year ago. At that time, Josh’s grades declined—largely because of missing assignments—and he has had several detentions because of being late to class. His father describes his son as increasingly fidgety, disorganized, and forgetful. During the seventh grade, Josh said he felt embarrassed about going to the school nurse’s office for his second methylphenidate dose. Josh was switched from short-acting methylphenidate to an extended-release formulation that he only took once, in the morning, before school. When asked about how he was tolerating the current medication, Josh responded: “I don’t like taking that stuff; it doesn’t do anything for me. My friends don’t have to take it.” Josh’s father adds, “Now that I think about it, we have at least two extra bottles full of pills at home. I don’t think Josh is taking it every day.”
Among adults with AD/HD, work and family are affected by inattention and poor short-term memory. Birthdays and anniversaries are forgotten, as are commitments to attend children’s school activities. Multiple auto accidents are also common. At work, projects may be initiated but remain uncompleted. Phone calls, coworkers, and e-mail all pose distractions that make it particularly difficult to get back “on track.”
Up to 80% of adolescents diagnosed with AD/HD continue to exhibit symptoms with a comparable adult rate of approximately 60%. Even when they no longer meet formal AD/HD diagnostic criteria, deficits are often present along with comorbid conditions, such as oppositional defiant disorder (ODD) or conduct disorder (CD) in adolescence and substance abuse, mood disorders and antisocial personality in adulthood. Among those adults with childhood histories that appear to remit, other psychiatric conditions are likely to emerge. Although findings have been mixed, there are indications that stimulant treatment during childhood reduces the likelihood of grade retention in school as well as the later development of comorbid psychiatric conditions, such as mood and anxiety disorders in adulthood.
CASE ILLUSTRATION 5: ADULT
Jim, a 35-year-old man, comes to see you after a particularly poor performance evaluation at work. Jim is an auto salesman who was recently promoted to manager of a small group of junior sales people. On his evaluation, Jim’s supervisor describes Jim as “ . . scattered, unable to set priorities; starts projects but doesn’t finish them; paperwork late or lost.” His supervisors describe him as a “nice guy” but “it’s hard to know what he wants; he contradicts himself a lot.”
At home, Jim’s wife took over the family’s schedule after Jim forgot several important dates, including her birthday. Many mornings, he dashes around the house looking for misplaced car keys. Jim’s wife has also become the primary disciplinarian of their two children because Jim had difficulty being consistent and following through with consequences.
Jim describes having a hard time getting through high school: “I did really badly on tests; I just couldn’t memorize.” Even in elementary school, “I was sent to the principal’s office for being the class clown.” College was a greater challenge. Jim had to repeat several classes and required an extra three semesters to graduate.
ETIOLOGY
Heritability for AD/HD is approximately 0.76. Adoption studies further support the strong role of genetics in the condition. Recent molecular genetic studies have attempted to locate specific neurotransmitter receptor sites. Specifically, genes coding for dopaminergic (DAT1, DRD4, and DRD5), serotonergic (5HTT and HTR1B
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