The children most likely to be diagnosed with attention-deficit/hyperactivity disorder are the obvious ones: stir crazy after a bit of time in the waiting room, in trouble at school, and bouncing off the walls at home.
It is children with the other face of ADHD–technically diagnosed as ADHD, predominantly inattentive type–who might be silently impaired and flying below the radar in your office and at school.
They are often diagnosed at older ages than children with ADHD predominantly characterized by hyperactivity and impulsivity, largely because their symptoms make them easy to overlook at school.
They don't get sent to the office, but might bring home report cards that seemingly fail to reflect their intelligence. Their work remains unfinished, and they seldom know the answer when called on in class. Yet if neuropsychological testing were performed, they would be likely to test in the normal range.
Research suggests that inattentive children might have an entirely separate diagnosis from those who better fit the official ADHD title, which incorporates “hyperactivity”–a feature they might not exhibit at all.
The likelihood of comorbid learning disorders is much higher in children with inattentive-type ADHD than with classically hyperactive children with ADHD–as high as 70% in some studies.
Among the third of children who “outgrow” ADHD, few are of the inattentive type, suggesting that the underlying neuroprocessing deficits in these children are more fixed.
The differential diagnosis for inattentive-type ADHD is broad and complex, akin to headache. Within it are physical problems, social stresses, and a variety of closely linked disorders that might be present as well, or masquerading as ADHD. The physician must consider each of these, then refer a child with suspected inattentive-type ADHD for neuropsychological testing to sort out subtleties within the processing and cognitive realms.
I begin with targeted hearing and vision screening because a child who cannot see the blackboard or hear the teacher is absolutely going to tune out. Next is the possibility–although unlikely–of absence (petit mal) seizures, which can look like inattention and have been known to persist for months without being diagnosed. Social preoccupation is the next major consideration on my list. Maybe the child isn't paying attention in school because she is thinking about her alcoholic father, depressed mother, sexual abuse, or consequences of misbehavior.
Language issues might complicate the diagnosis and may coexist with inattentive-type ADHD. If these are suspected, a referral to a speech and language specialist is critical. Cognitive ability might need to be formally tested as well. Perhaps the child is not inattentive, but simply does not have the intelligence to keep up in school as the material grows ever more complex.
Far and away, the most common missed diagnosis and frequent bedfellow of inattentive-type ADHD is anxiety. Although it feels like our practices are filled with children with ADHD, anxiety is a more common pediatric disorder. It is present in 12%-13% of the patients we see, compared with 4%-12% with ADHD. Anxiety is heritable and highly treatable, but may be interwoven with other disorders and difficult to tease out.
When I see combined anxiety/ADHD, inattentive type, I might treat the ADHD first, simply because response to stimulants is quicker and might enable a more comprehensive approach to the child's anxiety.
Keep in mind that medication management of ADHD children with predominantly inattentive type is somewhat different from the standard regimens for children with hyperactivity and impulsivity. The stimulant family is still often used first, but the most efficacious dose might be lower and trickier to spot, and initial choices should be the least anxiety-provoking medications. Some clinicians prefer with this population to try extended-release atomoxetine (Strattera).
With these children, I start low and go slow, getting frequent, objective feedback from parents and teachers to try to stop within a narrow window of maximum efficacy for inattention.
DR. HOWARD is assistant professor of pediatrics at the Johns Hopkins University School of Medicine, Baltimore, and creator of CHADIS, the Child Health and
Development Interactive System.