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Do QEEG Scan Results Differentiate ADHD From Other Psychiatric Disorders?
Data from this study are not yet published, but were presented at the recent annual meeting of the American Psychological Association (APA). Participants in the study were 209 individuals ranging in age from 6 to 30. Of the 209 participants, 177 had been diagnosed with ADHD, 16 with Oppositional Defiant Disorder (ODD), and 17 with a mood or anxiety disorder. The authors indicate that these were pure diagnostic groups, meaning that although members of each group may have displayed symptoms found in other psychiatric disorders, none met full diagnostic criteria for any disorder other than their primary diagnosis.
In order to determine whether the QEEG scanning process could differentiate patients with ADHD from those with other psychiatric disorders, Attention Index scores were computed for each participant as described above. The table below shows the average Attention Index scores for each diagnostic group across the different age ranges. Because there were relatively few individuals with ODD or an anxiety or mood disorder, these individuals were combined into a single group labeled Other Diagnosis in the table below. As noted above, higher Attention Index scores indicate high theta/beta ratios and are associated with more limited attention.
As indicated above, the average scores for participants with either the inattentive or combined subtype of ADHD are very similar to each other and substantially higher than the average score for participants with other psychiatric diagnoses. At each age level, the difference between the ADHD groups and the other diagnoses groups is statistically significant. The decline in Attention Index scores with advancing age is expected because the ability to maintain focused attention is an ability that typically increases with development.
When a criterion of 1.5 standard deviations above the mean for non-ADHD individuals was used as the cut-off between “normal” and “deviant” QEEG scan results, 78% of the ADHD group had scores in the deviant range. This means that the majority of individuals with ADHD have Attention Index scores that individuals without ADHD infrequently obtain. In contrast, 97% of individuals with other psychiatric diagnoses had Attention Index scores that fell within the normal range. Thus, although these individuals had a clear psychiatric disorder, their results on the QEEG scan were highly unlikely to fall in the range associated with ADHD.
Summary And Implications
This is a very important study. The results demonstrate that QEEG scan results indicative of high theta/beta ratios in prefrontal cortical areas are specific to ADHD, and are not likely to be found in those with other psychiatric conditions. In other words, the QEEG scan procedure is not only accurate in distinguishing between individuals with ADHD and “normal” individuals, but can also aid with differential diagnosis (i.e. distinguishing individuals with ADHD from those with other psychiatric problems). Because the differential diagnostic question is what clinicians typically face, it appears that this procedure has promise as a useful clinical diagnostic tool. This stands in sharp contrast to results recently reported for the Conners’ CPT, which was found to be of little value in distinguishing individuals with ADHD from those with other diagnoses.
Collectively, results from these studies provide strong support for QEEG scanning as an important technique for assisting in the diagnosis of ADHD. This does not mean, however, that this -- or any other individual test -- can be the sole basis for the diagnosis of ADHD. For example, in the studies reviewed here, between 10 and 20% of individuals who met standard diagnostic criteria for ADHD did not show abnormal QEEG results. In addition, a small number of participants who did not display the behavioral symptoms of ADHD did produce abnormal QEEG scans. These apparent errors point to the importance of basing an ADHD diagnosis on a variety of different data, obtained from a variety of sources. Thus, in addition to the benefits of an objective procedure such as QEEG scanning, information on children’s behavior collected from parents and teachers will always be a critical component of a thorough ADHD evaluation. It is also important to remember that a thorough evaluation for ADHD needs to include a broad assessment of an individual’s functioning so that other difficulties that often occur with ADHD -- or which may be present instead of ADHD -- are not missed.
Because a thorough diagnostic evaluation for ADHD requires this broad assessment of an individual’s functioning in addition to a specific focus on ADHD symptoms, in all likelihood there will never be a single test that is adequate for this purpose. Nonetheless, the QEEG scanning procedure examined in these studies appears to be an excellent tool for assisting clinicians in the evaluation of ADHD. Other research on this procedure has suggested that QEEG results also provide an accurate prediction of whether an individual will show a positive response to stimulant medication treatment. Thus, this technique may have important utility in treatment planning in addition to a role in the initial evaluation. In the upcoming years, it will be interesting to see whether QEEG scanning -- which is not yet in widespread use -- will begin to be implemented by a greater number of clinicians. For clinicians considering the possibility of incorporating this diagnostic aid into their work, the studies reviewed here certainly suggest there is a reasonable basis for doing so.
Note: This article originally appeared in Attention Research Update, an online newsletter written by Dr. David Rabiner, a Duke University psychologist and former member of CHADD's Professional Advisory Board. You can learn more about Attention Research Update and sign up for a free subscription at www.helpforadd.com.