NEW YORK CITY— While attention-deficit/hyperactivity disorder (ADHD) is typically thought of as a childhood disorder, adults are increasingly seeking treatment for symptoms that appear to be very similar to those seen in the younger population. And these are not new-onset cases, as a significant number of children with ADHD continue to meet the psychiatric criteria for the condition as adults, according to Rafael Klorman, PhD. He cited research showing that as many as 46% of children with ADHD continue to display symptoms of the disorder into adulthood.

“Because ADHD was first defined in children, there has been controversy as to whether there even is adult ADHD and, if it exists, what exactly it is,” said Dr. Klorman, Professor of Psychology and Director of Clinical Training in the Department of Clinical and Social Sciences in Psychology at the University of Rochester in New York. At an American Medical Association media briefing on ADHD, he sought to provide evidence that ADHD can continue into the adult years.

TRACKING THE CONTINUITY

“How do we know that ADHD continues into adulthood? The first line of evidence comes from following children who were diagnosed as having ADHD and continuing to evaluate them into the adult years,” explained Dr. Klorman. Between 4% and 8% of children evaluated in adulthood continue to meet the criteria for ADHD, he reported. “This may strike you as a bit low,” he acknowledged. “The rates I’ve been presenting, 4% to 8%, are actually an underestimate of the persistence of the disorder. The rates are higher, if you consider that some of these adults have partial symptoms of ADHD. If you consider partial manifestations of ADHD, then the rates rise to 11% or higher, depending on the study.”

The prevalence rates rise to 12% when the newer definitions of the disorder from the DSM-IV are applied, which include patients exhibiting primarily the inattentive-type elements of ADHD. Dr. Klorman continued, “As you may have gathered, evaluating an adult with ADHD presents a difficulty in that adults with ADHD are not the best informants—they tend to underdescribe the seriousness of their difficulties, so when ... parents are included in the evaluation of the young adults, the persistence of ADHD grows as high as 46%. These studies support the idea that ADHD continues into the adult years.”

COMORBIDITY IS COMMON

Additionally, adults with ADHD present with other problems related to the disorder. Dr. Klorman cited research showing that children who were diagnosed with ADHD, on average, complete two years less education than their peers. Not surprisingly, he added, and perhaps as a consequence, the types of jobs they hold as adults are quantitatively shown to be of lower prestige and lower earning potential. In terms of comorbidity, a large percent of these adults have had major depression. There is also an excess of antisocial personality disorder and some evidence for increased rates of a history of substance use as well as some findings for an elevation of anxiety disorders. Adults with ADHD have more frequent traffic tickets, accidents,and suspensions, and they perform more poorly than do controls when operating an objective-driving simulator. When all substances—drugs, alcohol, and smoking—are considered, in one study 55% of adults with ADHD had a history of substance abuse versus 27% of controls, he said. However, when seen in adulthood, patients with ADHD do not have a higher prevalence of substance abuse than controls, he noted.

SUPPORTING EVIDENCE

Additional evidence for the existence of ADHD in adulthood comes from adults who seek diagnosis or treatment but were not necessarily evaluated or treated in childhood, Dr. Klorman said. “The diagnostician’s problem with this is to ascertain, with conviction, that in fact they meet the criteria for ADHD, and those are the patients who have been studied.” He elaborated, “One question is how to translate the 18 symptoms of ADHD, defined for a population of children and teenagers, into appropriate corresponding symptoms for adults,” he said. “Another area of controversy is whether we should be using the same number of symptoms to determine our diagnosis when we move to adults. Children must display six or more of the 18 symptoms to be diagnosed with ADHD, but some people who work with adults think that it may be appropriate to diagnose an adult on the basis of as few as three or four.

“Unfortunately, we only know about people who come in for treatment—we know a whole lot less about people who don’t. Sadly, the pervasiveness of the consequences of ADHD into the adult years for a community sample certainly includes people who haven’t been treated.”

CONTINUED EFFECTIVENESS OF MEDICATION

Another line in support of the idea of ADHD in adults, according to Dr. Klorman, is that “the same medications we know to be effective—based on double-blind clinical trials—in children with ADHD are effective for adults with ADHD. This is consistent ... with the proposition that this is a condition that continues into the adult years.” The stimulants that are most commonly used in children have demonstrated very high response rates in adults.

EXECUTIVE FUNCTION IS AFFECTED

Dr. Klorman believes that “adults with ADHD present the same types of cognitive problems as do children with ADHD. There is consensus in the field that executive functions are deficient in these children, and we can administer tests that formally evaluate deficits in executive function.” Although these tests are not sensitive or specific enough to be used for diagnosis, in terms of testing sample populations they help delineate the kind of problems seen in adults with ADHD.

Focusing on two aspects of executive function, Dr. Klorman explained that “one of the requirements of life is to shift from one priority to another, from one dimension to another, depending on what the situation calls for.” Accordingly, a commonly used test of shifting, the Wisconsin Card Sorting Test, is administered to children with ADHD who do well until they are asked to shift the concept used for sorting (eg, from color to number or shape) at which point they have more difficulty than their peers. “The interesting thing about this task is that it is particularly difficult for patients with lesions in the frontal lobe, which of course are involved in executive function, and adults with ADHD also have trouble with shifting,” he observed. Also, the Stroop Task test presents difficulty for both children and adults with ADHD, as it requires the participant to inhibit his or her ability to read when naming the color of the ink in which words describing colors are printed. In this test, the color and word are inconsistent with each other (eg, the word RED printed in blue).

The aspects of cognitive function revealed by these tests are known to be regulated by the prefrontal lobes and basal ganglia, circuitry that is relatively well understood. “There is emerging imaging research that indicates that precisely those three structures are less active when ADHD adults and children take these tests, and that stimulant medications increase brain activation in those three areas for adults and children with ADHD.”

RESTATING THE CASE

There were four points on which Dr. Klorman based his foundation for recognizing ADHD in adults, which he summarized: “ADHD in adults is real and a similar disorder to that which we have studied in children for years. First is the continuity that has been observed in children followed up through the adult years; second is the similarity in the behavioral and psychiatric problems with ADHD with children [and adults]; third, the similarities in the effects of therapeutic agents; and lastly, similarities in executive dysfunction.”

Research efforts should be focused, according to Dr. Klorman. “We need to continue to pursue imaging and other research avenues that will improve our ability to diagnose ADHD quickly and easily. In addition, we need to better understand those patients who do seem to outgrow ADHD. We would like to know whether the improvement represents a remission of the disorder or whether some people are successful at developing ways to cope.”

—Heidi W. Moore

Suggested Reading
Faraone SV, Biederman J, Spencer T, et al. Attention-deficit/hyperactivity disorder in adults: an overview. Biol Psychiatry. 2000;48:9-20.
McLean A, Dowson J, Toone B, et al. Characteristic neurocognitive profile associated with adult attention-deficit/hyperactivity disorder. Psychol Med. 2004;34:681-692.
Woods SP, Lovejoy DW, Stutts ML, et al. Comparative efficiency of a discrepancy analysis for the classification of attention-deficit/hyperactivity disorder in adults. Arch Clin Neuropsychol. 2002;17:351-369.

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