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Experts highlight cognitive symptoms of ADHD, efficacy of available treatments

Thursday, December 13 2007 | Comments
Evidence Grade 0 What's This?
In addition to behavioral symptoms, attention-deficit/hyperactivity disorder is also associated with cognitive deficits, but currently available pharmacotherapies for ADHD can successfully treat many of the disorder's cognitive symptoms, according to experts.

Ronna Fried, director of paradigm development at Massachusetts General Hospital, highlighted several cognitive aspects of ADHD, with particular emphasis on executive function deficits.

The term "executive function" refers to multiple primary processes, Fried explained. Specifically, she noted that executive functions are the mental operations involved in goal-directed behavior and self-regulation. Of the 8 different executive function domains, Fried highlighted 4 that involve both cognition and behavior: set-shifting (the ability to move easily from one situation, activity, or aspect of a problem to another), planning/organizing, working memory, and inhibition.

Executive function deficits are common in ADHD, but they are not present in all cases of ADHD nor are they unique to individuals with ADHD, Fried added. She cited research in which adults with executive function deficits, ADHD, or both were compared with adult controls. Researchers found that adults with ADHD were more likely than were controls to experience psychometrically defined executive function deficits (31% vs 16%). In addition, individuals with both ADHD and executive function deficits had significantly greater impairments in interpersonal functioning and a particularly high risk of occupational and academic underachievement. Similar results have been observed in pediatric populations, Fried added.

Although measures of executive function cannot be used to make an ADHD diagnosis, various tests and self-report checklists assessing executive function may help guide treatment decisions. For example, assessments of set-shifting, planning/organizing, and inhibition include the Trail-Making Test Part B, the Rey-Osterrieth Complex Figure Test, and the Stroop Color-Word Test, respectively. Fried said she has also used the Behavior Rating Inventory of Executive Function (BRIEF) to measure executive function in adults with ADHD, but cautioned that it cannot really be used in clinical practice.

"[T]he neuropsychological tests I believe really help with the treatment planning, because they fine-tune what the intervention should be, both for children and for adults," she concluded.

Dr. Timothy Wilens, director of substance abuse services in Massachusetts General Hospital's Pediatric Psychopharmacology Clinic, explained that drugs approved for ADHD may have important effects on cognition. He noted, however, that there is a limited amount of psychopharmacologic research evaluating neuropsychological deficits in ADHD.

Among the existing evidence, Dr. Wilens continued, some studies have shown that immediate-release methylphenidate improves response inhibition, visuospatial span, and spatial working memory in patients with ADHD. Other studies have shown significant improvement in attention (assessed with the Swanson, Kotkin, Agler, M-Flynn, and Pelham attention subscale) with OROS methylphenidate, with methylphenidate administered 3 times daily, and with the methylphenidate transdermal system as compared with placebo. Additional research has also shown significant improvements in attention (assessed with the Connors' ADHD Rating Scales--Teacher and Parent Versions [inattentive subscale]) with d-methylphenidate and improvements in processing speed (assessed with Stroop Color Test T-scores) and inhibitory capacity with atomoxetine.

Dr. Wilens is currently leading a trial to evaluate OROS methylphenidate plus atomoxetine in patients who have shown a partial response to atomoxetine monotherapy. So far, 40 patients have exhibited improvements in ADHD Rating Scale scores (measured as percent change) as well as significant improvements in BRIEF inhibition T-scores, shifting T-scores, and initiation T-scores relative to baseline and 4 weeks of atomoxetine monotherapy.

With careful monitoring of patients, Dr. Wilen concluded, "[Y]ou can see very prominent effects on attention that vary not only by class of medication but by the delivery system of medication, very subtle differences that you can pick up in attention."

This information concerns uses that have not been approved by the Food and Drug Administration.

By Shayna Muckerheide

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