Symposium Report: Current opinion on management of neurologic disorders

CHALLENGES AND CONTROVERSIES
IN DIAGNOSING ADULT ADHD

The notion that attention-deficit/ hyperactivity disorder (ADHD) can persist through adulthood has generated both controversy and, more recently, a growing body of clinical research. Since the pioneering work of Paul Wender, MD, and colleagues in the 1970s, numerous longitudinal studies and clinical trials have documented ADHD in late adolescence and adulthood, and record numbers of adults have sought evaluation and treatment. However, validated diagnostic criteria are still lacking for postadolescents, according to James J. McGough, MD, Associate Clinical Professor of Psychiatry and Biobehavioral Science at the University of California, Los Angeles. No adults were included in the ADHD field trial for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), and the subtypes defined in the DSM-IV (inattentive, hyperactive, and combined) have never been validated in adults, Dr. McGough said.

As a result, the obstacles that clinicians currently face when assessing adult patients who may have ADHD include developmentally inappropriate diagnostic criteria, changes in symptoms as patients age, and the possibility that high intelligence or situational factors can mask symptoms. The high incidence of comorbid conditions can further complicate diagnosis.

WHY CURRENT CRITERIA MAY BE INADEQUATE

Although the DSM-IV criteria are successful in identifying some adults with ADHD, they may not be sufficiently sensitive to identify all those who would benefit from clinical assistance, Dr. McGough suggested. Assessment of adult ADHD is generally based on semistructured interviews to establish current impairment, as well as a retrospective review of childhood symptoms. The DSM-IV criteria require the presence of at least six of nine specified symptoms of inattention, or at least six of nine hyperactive impulsive symptoms, persisting for a period of six months.

The symptoms listed in the DSM-IV, however, are based on observations of school-age children, and some may not be applicable to adults, Dr. McGough observed. Notable examples include "running and climbing excessively" or having "trouble playing quietly." Other symptoms may not be apparent in affected adults because work or social environments may not provide opportunities to exhibit them; "talking obsessively," for example, may not be a noticeable problem for a person who works alone in a home office. Thus, the pool of potential symptoms is smaller for adults than for children, and it may be more difficult for adults to meet the threshold of six symptoms required by the DSM-IV criteria.

Moreover, although there is growing evidence that the number of ADHD symptoms exhibited by adult patients diminishes with time, the functional impairment caused by remaining symptoms often continues or even increases. "You may lose symptoms, but life gets harder," explained Thomas J. Spencer, MD. Thus even if a patient has fewer symptoms than he did as a child—and no longer meets current diagnostic criteria—the effects "may be more devastating at this point," according to Dr. Spencer, who is Associate Professor of Psychiatry at Massachusetts General Hospital. Indeed, a study led by Russell Barkley, MD, of the University of Massachusetts Medical Center, demonstrated functional impairment in adults with much lower levels of symptoms than those mandated by the DSM-IV.

Furthermore, the nature of the ADHD symptoms that do occur may change during adulthood. "Perhaps there are other symptoms that these patients are exhibiting which are equally impairing but are not in the DSM-IV list," Dr. McGough proposed. For example, adults with ADHD typically have problems with work, marital relationships, parenting, and finances, but none of these domains are represented by the DSM-IV criteria. In addition, various affective symptoms, such as irritability, difficulties in managing frustration, and being overly sensitive to criticism, have been reported to occur in adults with ADHD.

Yet another drawback to the DSM-IV criteria is the requirement that symptoms be present before the age of 7. A 45-year-old man, for example, is unlikely to remember, four decades later, precisely when his problems with attention became apparent, Dr. McGough noted. Moreover, the DSM-IV field trial itself found that about 40% of children diagnosed with the inattentive subtype did not manifest impairments until the age of 8 or 9. "So it is difficult to maintain that the age 7 cutoff is reasonable," Dr. McGough contended. Inattentive symptoms may not become apparent until academic or other demands bring them out, he added.

INTELLIGENT BUT INATTENTIVE

Yet another obstacle to diagnosis, according to Dr. McGough, is that many individuals—particularly those with high intelligence—often develop selective coping strategies that may mask ADHD-related impairments; such individuals may perform adequately in school as children but meet with difficulties during college and adulthood. This theme was further developed by Thomas E. Brown, PhD, Assistant Clinical Professor of Psychiatry at Yale University School of Medicine. Some adults seek evaluation and treatment for ADHD despite having attained apparent career success—even completing law or medical degrees—because they feel that they are not reaching their potential in their jobs and social relationships, Dr. Brown said. Study of these highly intelligent individuals, according to Dr. Brown, not only provides an opportunity to assess ways in which ADHD impairments interfere with cognitive functions but may shed light on the neuropsychological nature of ADHD.

Dr. Brown and Yale colleague Donald Quinlan, PhD, collected data on 103 adults with ADHD (ages 18 to 63) who scored 120 or above on the Wechsler Adult Intelligence Scale-Revised, placing them in the top 9% of the population. Most of the patients were male (72%) and had predominantly inattentive or combined-type ADHD.

Nearly all of the subjects were high school graduates, while 56% had earned a bachelor's degree and 22% had completed a doctoral degree in medicine, law, or other fields. Yet 42% had dropped out of postsecondary education at least once, and some had returned and dropped out multiple times because of difficulty meeting academic requirements. A similar proportion of the patients (41%) were significantly underemployed at the time of evaluation, often working in unskilled jobs.

"Despite their superior IQ, many subjects showed impairments on IQ subtests sensitive to attention and concentration problems relative to their high scores on other verbal subtests," Dr. Brown reported. For example, on a test of verbal memory (the Wechsler Memory Scale-Revised Logical Memory I), 77% of subjects scored below the 60th percentile and 23% scored below the 25th percentile.

A REFLECTION OF EXECUTIVE DYSFUNCTION?

Rarely were these individuals' difficulties related to hyperactivity or impulsivity, according to Dr. Brown. Rather, the reported symptoms—including problems in organizing and prioritizing work, filtering out distractions, managing frustration, and using short-term memory—significantly overlap with the neuropsychological construct of executive function, or central control processes, Dr. Brown noted. In fact, he said, these and other findings suggest that ADHD might best be characterized as a disorder of executive functions. Most of the subjects (88%) scored in the severely impaired range on the Brown ADD Rating Scale for Adults, a 40-item self-report scale that reveals impairments in five clusters of executive functions associated with ADHD. This concept—impaired executive function—could help explain why some ADHD symptoms appear only when academic or other complex intellectual demands increase.

Significantly, all of the subjects reported that they could concentrate quite well during a few selected activities, particularly those that they found especially interesting. "That's the giveaway," Dr. Brown said. "These are not problems with the basic [cognitive] modules, because sometimes they work well." Nor does the prevailing model of ADHD—which posits that the core of the disorder is a lack of behavioral inhibition—adequately account for these patients' problems, Dr. Brown said; their difficulties with activation, orientation, motivation, and vigilance all point again to disordered executive function.

Viewing his subjects' plight metaphorically, Dr. Brown noted that just as an orchestra of expert musicians may not perform well if they lack a strong conductor, intelligent adults with ADHD may show superior performance on many cognitive subfunctions but be unable to manage their lives cohesively. These adults may be misdiagnosed if a clinician relies on simple cognitive tests, he continued, because "executive function, by definition, involves the simultaneous management of a variety of different functions. It would seem that the complex tasks of daily life—how well a person can manage their work, shop for groceries, clean their house, care for their children—are far more sensitive diagnostic indicators than most of the instruments we have at this time." Thus, the most important aspect of making an accurate diagnosis, he said, is "a well-done clinical history by someone who knows what this disorder looks like and can differentiate it from others."

OVERLAPPING SYMPTOMS

An additional factor that can hinder diagnosis of ADHD in adults is the high prevalence of comorbid psychiatric conditions, including depression, anxiety, substance abuse, and personality disorders. However, the key is a thorough clinical history, according to Lily Hechtman, MD, of McGill University in Montreal. Although it is difficult, reconstructing the patient's childhood behavior can be enormously helpful, she said, because subsequent comorbid conditions often overshadow ADHD symptoms. School records and teacher comments from report cards can help identify early manifestations of ADHD; so can reports from parents or siblings, although these are subject to the biases and failures of memory.

Knowing the patient's family medical history is also helpful in making a diagnosis. "If the patient has a family history of bipolar disorder and does not have a childhood history of ADHD, you may in fact be dealing with bipolar disorder," Dr. Hechtman said.

Comorbid symptoms often appear later in life, years after ADHD symptoms become apparent, and may be unrelated to ADHD. While both conditions may need to be treated, "the process of untangling what is primary and what is secondary is not easy, and overlapping symptoms can make this distinction problematic," Dr. Hechtman warned. The clinical history can provide clues, but ultimately the clinician "needs to determine which are the most impairing symptoms that the person has and address those first."

Among specific disorders, the rates of anxiety and depression observed in adult ADHD populations vary substantially, not differing from controls in some studies but reaching as high as 30% in others. "It is up to you to decide whether ADHD is the cause of those impairments," said Dr. Spencer. "If they had social problems at age 30 and then became depressed, it is unclear that giving them [methylphenidate] will help their social problems."

Oppositional defiant behavior is also common in adults with ADHD. Often, patients taking medication report no improvement in their condition, Dr. Spencer noted, whereas the spouse notices that oppositional symptoms are no longer present. Other comorbid conditions, such as bipolar disorder, antisocial personality, substance abuse, and mania have also been reported to occur in adult ADHD, but to a lesser degree. Comorbidity rates in men and women appear fairly similar, except in the cases of conduct disorder, bipolar disorder, and substance abuse, Dr. Hechtman said.

Uncovering the biological correlates of ADHD symptoms may help clinicians disentangle ADHD from comorbid conditions; neuroimaging studies of adults with ADHD have reported abnormal activation of the frontal cortex and subcortical structures, Dr. Spencer noted. In addition, the identification of candidate ADHD genes, particularly those that play a role in the dopamine system, has opened up another area of study that may aid diagnosis and treatment.

However, until the deficiencies of current diagnostic criteria are addressed, Dr. McGough noted, "we risk underdiagnosing [ADHD in adults] and missing people who are really impaired. We may overdiagnose in some instances and medicate in a way that is inappropriate. We can misdiagnose by confusing one thing for another, and it is not uncommon for psychiatrists to miss ADHD in adults completely and focus on a mood disorder. As a result of all of this," he concluded, "we really risk inadequate and inappropriate treatments."

—Shauna Kubose
Senior Associate Editor

Suggested Reading

Barkley RA. Attention-Deficit Hyperactivity Disorder, A Handbook for Diagnosis and Treatment, 2nd ed. New York, NY: Guilford Publications;1998.

Denckla MB. Biological correlates of learning and attention: What is relevant to learning disability and attention-deficit hyperactivity disorder? J Dev Behav Pediatr.1996;17:114-119.

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