ADHD Grows Up
Adult Diagnosis Can Be Especially Tough

by Thomas S. May

September, 2006

Attention-Deficit/Hyperactivity Disorder, or ADHD, conjures images of young children jumping up and down, running around in the classroom, and not being able to concentrate on their schoolwork. But ADHD affects adults, too: the majority of children with the disorder never outgrow it.

Adults with ADHD often have difficulty finding or keeping a job, and they frequently experience problems in their social relationships as well. Studies also show that a large percentage of adults with ADHD develop addictions or major depression, and a disproportionately large number get into traffic accidents or run into legal problems. 

Diagnostic Dilemma

Currently, there is no gold standard or laboratory test to confirm the diagnosis of ADHD, so physicians must rely on behavioral characteristics when making a diagnosis, says Christopher Kratochvil, an associate professor in the department of psychiatry at the University of Nebraska Medical Center. At this year’s annual meeting of the American Psychiatric Association, held in May in Toronto, he listed several reasons why ADHD in adults may go undiagnosed and untreated.

Historically, physicians—including psychiatrists—have received limited training in diagnosing and treating ADHD in adults, he said. Doctors may not be aware that, while children usually show overt hyperactivity, aggressiveness, and low frustration tolerance, grownups rarely show these symptoms.

Instead, adults with ADHD may be restless, impatient, and become bored easily, Kratochvil said at the Toronto meeting. Because these characteristics are quite common and seem fairly innocuous, some physicians may be reluctant to make a diagnosis and prescribe treatment such as stimulant medication, he added.

What makes diagnosing adults with ADHD especially hard is that, in the current (fourth) edition of the Diagnostic and Statistical Manual (DSM-IV) of psychiatric disorders, all clinical descriptions and diagnostic criteria relating to ADHD are based on children, points out Stephen Faraone, a professor of psychiatry at State University of New York in Syracuse.

Even when diagnosing adults, clinicians must consider symptoms that do not apply, such as “often leaves seat in classroom,” Faraone says. “Developmentally sensitive criteria may be needed to fully capture the range of adult ADHD in the population,” he says.

Clues in the Brain

Although symptoms tend to be different in children and adults, ADHD appears to be caused by the same neurochemical disturbances. For example, neuro­imaging studies of both children and adults have found decreased availability of the neurotransmitter dopamine inside a part of the brain called the striatum.

Recent studies suggest other important brain differences in both children and adults. For example, George Bush, an assistant professor of psychiatry at Harvard Medical School, and colleagues have a paper in press that shows that a part of the brain called the anterior cingulate cortex (ACC) is approximately 13 percent smaller in people with ADHD. In a separate study currently being reviewed, the same researchers found that cortical (gray matter) thickness is significantly less in the “attention network” (ACC, dorsolateral prefrontal cortex, and parietal cortex) of unmedicated adults with ADHD, compared to matched controls.

Despite the fact that neuroimaging studies consistently show that people with ADHD have certain unique variations in brain structure and function, neuroimaging cannot yet be used to diagnose ADHD, Bush cautions. But that may change in the not-too-distant future.

Developing an objective test for ADHD could be a very important step that might help millions of children and adults be properly diagnosed—and obtain appropriate treatment—for this “distinct and truly disabling disorder,” Bush says.