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Neuropsychiatry Reviews

Vol. 1, No. 1
February 2000


ADHD IN ADULTS: ARE THE CURRENT DIAGNOSTIC CRITERIA ADEQUATE?

CHICAGO—The notion that attention-deficit/hyperactivity disorder (ADHD) can persist through adulthood has generated both continued controversy and a growing body of research. While some experts continue to question the existence of adult ADHD, others have shifted their focus to determining how best to define it. In a symposium at the 46th Annual Meeting of the American Academy of Child and Adolescent Psychiatry, researchers discussed the limitations of applying the current ADHD diagnostic criteria to adults and presented findings that challenge the prevailing view of the disorder.

Since the 1970s, longitudinal studies and clinical trials have documented ADHD in late adolescence and adulthood, and record numbers of adults have sought evaluation. However, validated diagnostic criteria are still lacking for postadolescents, according to James J. McGough, MD, an 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 not been validated in adults, Dr. McGough said. As a result, the obstacles that clinicians face when assessing adults who may have ADHD include developmentally inappropriate diagnostic criteria, age-related changes, comorbidities, and the possibility that high intelligence or situational factors can mask ADHD symptoms.

ARE CURRENT DIAGNOSTIC CRITERIA INADEQUATE?

Although the DSM-IV criteria identify some adults with ADHD, they may not be sufficiently sensitive to identify all individuals who need clinical assistance, Dr. McGough said. Assessment of adult ADHD is generally based on semistructured interviews to establish current impairment, as well as on a retrospective determination of childhood symptoms. The DSM-IV criteria require that a person exhibit at least six of nine specified symptoms of inattention, or at least six of nine hyperactive impulsive symptoms, for a period of six months.

These criteria, however, are based on observations of school-age children, and some may not be applicable to adults (eg, "running and climbing excessively" or having "trouble playing quietly"). Other symptoms may not be apparent in adults because the individual's work or social environment provides no opportunities to exhibit them; "talking obsessively," for example, is unlikely to be a 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 them to meet the threshold of six symptoms required by the DSM-IV criteria.

Also, although there is growing evidence that adults exhibit fewer ADHD symptoms with time, the impairment caused by the 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 the criteria for ADHD—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 said. Adults with ADHD typically have problems with work, marital relationships, parenting, and finances; however, none of these domains are represented by the DSM-IV criteria. Also, various affective symptoms, such as irritability, difficulties in managing frustration, and being overly sensitive to criticism, reportedly occur in adults with ADHD.

Yet another drawback to the DSM-IV criteria is the requirement that symptoms appear before age 7. A 45-year-old man being evaluated for ADHD for the first time is unlikely to remember 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 age 8 or 9. "So it is difficult to maintain that the age 7 cutoff is reasonable," Dr. McGough said. Inattentive symptoms may not become apparent until academic or other demands bring them out.

INTELLIGENT BUT INATTENTIVE

Yet another obstacle to diagnosis is that many individuals—particularly those with high intelligence—develop coping strategies that mask ADHD impairments; they may perform adequately in school as children but meet with difficulties during college and adulthood. Thomas E. Brown, PhD, assistant clinical professor of psychiatry at Yale University School of Medicine, noted that some adults seek evaluation and treatment for ADHD despite apparent career success—even completing law or medical degrees—because they feel they are not reaching their potential in their jobs and social relationships. These intelligent individuals, noted Dr. Brown, not only provide an opportunity to assess ways in which ADHD impairments interfere with cognitive functions but may shed light on the neuropsychologic 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 in terms of intelligence. Most of the patients were male (72%) and had predominantly inattentive or combined-type ADHD. Nearly all were high school graduates, while 56% had a bachelor's degree and 22% had a doctoral degree in medicine, law, or other fields. Yet 42% had dropped out of postsecondary education at least once; some had returned and dropped out multiple times because of difficulty meeting academic requirements. A similar proportion of subjects (41%) were significantly underemployed at evaluation, often in unskilled jobs.

"Despite 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 symptoms reported by the subjects—including problems in organizing and prioritizing work, filtering out distractions, managing frustration, and utilizing 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 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. Furthermore, impaired executive function helps explain why some ADHD symptoms appear only when complex intellectual demands increase.

All of the subjects could concentrate well during a few selected activities, particularly those that they found 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.

Just as an orchestra may not perform well without a strong conductor, intelligent adults with ADHD may show superior performance on many cognitive subfunctions but be unable to manage their lives cohesively. These individuals may be misdiagnosed if a clinician relies on simple cognitive tests, Dr. Brown warned, 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." 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."

THE PROBLEM OF OVERLAPPING SYMPTOMS

Another 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 to success is again a thorough clinical history, which can help distinguish ADHD from other disorders, according to Lily Hechtman, MD, of McGill University in Montreal. Although 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. The patient's family medical history is also helpful. "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 and not ADHD," Dr. Hechtman said.

Comorbid symptoms often appear later in life, years after ADHD symptoms became apparent, and may be unrelated to the patient's 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 the clinician "needs to determine which are the most impairing symptoms that the person has and address those first."

The rates of anxiety and depression observed in adult ADHD populations vary, 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 Ritalin will help their social problems."

Oppositional defiant behavior is also common in adults with ADHD. Often, patients taking medication report no improvement, Dr. Spencer noted, whereas their spouse disagrees because the oppositional symptoms are no longer present. Other comorbidities, such as bipolar disorder, antisocial personality, substance abuse, and mania have also been reported to occur in adult ADHD patients, but to a lesser degree. Comorbidity rates in males and females 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 better allow clinicians to 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 may eventually 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, we really risk inadequate and inappropriate treatments."

—Shauna Kubose

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

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