Attention Research Update

February 2005

"Helping parents, professionals and educators stay informed about new research on ADHD"

David Rabiner, Ph.D.  Senior Research Scientist, Duke University


ADHD, Executive Functioning, and Academic Achievement

Although ADHD can create difficulties in many areas of a child's life, the adverse impact it frequently has on academic functioning is especially problematic.  This has been documented in numerous studies, where it has been shown that children with ADHD are less likely to complete high school, more likely to repeat a grade, more likely to be placed in special education classes, and less likely to achieve to their potential.

Despite this general pattern of findings, not all children with ADHD experience significant academic struggles.  In fact, a number manage to do reasonably well despite the disorder.  What might account for the wide range of variability in academic outcomes for children with ADHD?  Why do some achieve reasonable levels of academic success while many others struggle mightily, regardless of how bright they may be?

One factor that may help explain the variability in academic outcomes in children with ADHD is the presence vs. absence of executive functioning deficits (EFDs).  Executive functions (EFs) can be thought of as the decision-making and planning processes that help to control and direct our behavior.  For example, when a child has a long-term assignment to complete, the executive functioning tasks involved would include dividing the task into sub-task, making a plan for completing those tasks, and monitoring performance along the way. Although no single list of EFs is universally agreed upon, most experts would agree that important EFs include such abilities as planning, reasoning, working memory (i.e., holding information in memory for later use), inhibiting behavior that may bring immediate rewards in pursuit of a long-term goal, some aspects of attention, and shifting cognitive sets, i.e., flexibility in thinking. 

These EF skills are believed to be critically important for complex human behavior because they serve to organize and guide behavior in flexible and adaptive ways. A number of studies have demonstrated that children with ADHD exhibit EFDs relative to children without the disorder.  In fact, current conceptualizations of ADHD emphasize that EFDs may represent the core deficits associated with ADHD, and that symptoms used to define the disorder - inattention and hyperactivity-impulsivity - are the result in many instances of these core EFDs.

Despite the important role that EFDs play in current theorizing about ADHD, very little is known about the clinical implications of EFDs in children and adolescents with ADHD.  For example, there has been little research on whether EFDs and core ADHD symptoms contribute independently to academic difficulties as well as the other problems that many children/teens with ADHD experience.  In fact, one distinct possibility is that in the absence of EFDs, children with ADHD may not experience the severe academic struggles that are regularly associated with the disorder. 

If this were found to be true, then routinely assessing children with ADHD for EFDs could alert parents and clinicians to when academic problems are especially likely to develop.  This knowledge could enable them to make extra efforts to prevent this from occurring. It is also possible that ADHD with and without EFDs is associated with different outcomes in other important emotional and behavioral domains and this could also have important implications for treatment planning.

This interesting issue was the focus of a study published recently in the Journal of Consulting and Clinical Psychology (Biederman et al., (2004). Impact of executive function deficits and attention deficit/hyperactivity disorder on academic outcomes in children. JCCP, 72, 757-766.  Participants in this study were children and adolescents with (n=259) and without (n=222) ADHD.  Unlike many studies in the literature, girls and boys were represented in relatively equal numbers. 

Participants ranged in age from 6-17 and received a variety of assessment measures in the study. These included:

  • psychiatric assessments to establish the ADHD diagnosis as well as the presence of co-occurring emotional and behavioral disorders;
  • psychosocial assessments to assess social difficulties at school and in interactions with peers, siblings, and parents;
  • cognitive assessments to assess IQ and academic achievement level in reading and math; and
  • neuropsychological assessments specifically intended to assess key elements of executive functioning.  The neuropsychological battery included 6 measures to assess a range of EFs including planning and organizational skills, reasoning, cognitive flexibility, working memory, ability to inhibit impulsive responding, and certain components of attention.

For each EF tested, participants were classified as having a deficit if their performance fell in the bottom 7% for children/teens who comprised the non-ADHD sample.  Participants were then classified as having an overall EFD if they scored in this range on 2 or more of the EFs that were assessed.  Participants who scored poorly on 1 or fewer EF measure were considered "normal" in regards to their overall executive functioning.  The rational behind this classification procedure is that whereas impaired performance on only a single neuropsychological test may be due to chance, two or more impaired tests would likely be interpreted as a deficit by most clinicians.

Participants' classification as EFD vs. non-EFD groups was combined with their diagnostic status for ADHD to form 4 groups: control participants without EFD (n=196); control participants with EFD (n=26); ADHD without EFD (n=173); and ADHD with EFD (n=86).  Once these groups were identified, the researchers examined how they compared on the academic, social, and psychiatric outcomes that were assessed.  As noted above, they were especially interested in whether EFDs in children/teens with ADHD was reliably associated with poorer academic, psychiatric, and social functioning.


RESULTS

The researchers first tested whether EFDs were more common in children and teens with ADHD than in control participants.  Thirty-three percent of participants with ADHD had EFDs compared to only 12% of control participants; this difference was statistically significant.

Next, they examined whether particular clinical aspects of ADHD were associated with EFDs.  Participants with ADHD and EFDs did not differ from those with ADHD but without EFDs in their age of onset of ADHD or the number of hyperactive-impulsive symptoms.  They did, however, have slightly more inattentive symptoms, but the average difference was not large (i.e., less than 1 symptom).

EFDs and Academic Functioning

As expected, children with ADHD showed poorer academic performance in a variety of areas compared to control children; this was true regardless of whether or not control children had EFDs.  Of greater interest, however, is that within the group of participants with ADHD, the presence of EFDs was strongly and consistently associated with poorer academic performance. 

Compared to participants with ADHD and no EFD, those with ADHD + EFD were more likely to have repeated a grade (42% vs. 19%), to be diagnosed with a learning disability (44% vs. 20%), to have lower IQ scores (98 vs. 109), and to have lower achievement in math (85 vs. 99) and reading (92 vs. 106).  (Note that for IQ and the achievement scores, the average score is 100.)  The differences found for grade retention, learning disability, and achievement in reading and math were evident even after controlling for IQ, SES, and medication status, which suggests that EFDs were the critical variable accounting for the differential performance.  Among children without ADHD, those without EFDs tended to perform better, but the differences were not as pronounced and were generally not significant.

EFDs and Other Outcomes

In regards to the other areas assessed, the association between EFDs, ADHD, and negative outcomes was different.  Specifically, although participants with ADHD had more negative outcomes than control participants in virtually all areas, the presence EFDs within the ADHD group did not appear to make a difference.  Thus, both groups of participants with ADHD - i.e., those with EFDs and those without - had similar rates of mood disorders (34% vs. 37%), anxiety disorders (32% vs. 40%), disruptive behavior disorders (53% vs. 55%), substance use (10% vs. 9%), and smoking (13% vs. 13%). Except for substance use, these rates were all substantially higher than those reported for control participants, and in no instance did they differ significantly from one another.  In regards to the overall measure of social functioning, participants in the 2 ADHD groups were again equivalent and had significantly more difficulties than control participants.


SUMMARY and IMPLICATIONS


Results from this study suggest that EFDs are significantly more common in children/teens with ADHD than in those without the disorder, and that among individuals with ADHD, EFDs increase the risk for grade retention, learning disability, and lower academic achievement. 

Furthermore, the greater academic difficulties experienced by children with ADHD who also have EFDs  cannot be explained by differences in IQ, SES, medication status, or in the greater severity of core ADHD symptoms.  Thus, it appears that EFDs may make an independent contribution to academic problems above and beyond those related to the core symptoms of ADHD alone.

In regards to other psychiatric outcomes and overall social functioning, however, there was no indication that EFDs add to the difficulties that are associated with ADHD alone.  The authors note that this does not necessarily mean that EFDs do not add to the risk posed by ADHD in regards to these other negative outcomes.  Instead, it is possible that when EFDs are present along with ADHD, it may take longer for this additional risk to become evident, whereas for academic difficulties, the negative impact occurs earlier in development.  This, of course, is a hypothesis that would require additional study in order to test.

These findings have potentially important clinical implications in that only about 1/3 of participants with ADHD also had EFDs as defined by the researchers.  If these findings were replicated, it would provide a strong indication that routinely screening children newly diagnosed with ADHD for EFDs could be an important addition to ADHD evaluations protocols.  To my knowledge, such screening is not typically done, particularly when the diagnosis is being made by primary care physicians who are not generally trained to administer and interpret neuropsychological tests.

The benefit of this screening is that by identifying those children with ADHD who also showed EFDs, more intensive efforts to prevent the development of academic struggles could be initiated.  As the authors note, because it is not clear how EFDs respond to standard pharmacological treatment for ADHD, children with ADHD and EFDs may require additional academic intervention to prevent academic failure; they may also required a different type of intervention that is specifically designed to address their executive functioning deficits.  Developing and evaluating such intervention efforts remains an important topic for subsequent research in this interesting and important area.


Information presented in Attention Research Update is for informational purposes only, and is not a substitute for professional medical advice.  Although newsletter sponsors offer products and services that I believe will be of interest to subscribers, sponsorship of Attention Research Update does not constitute a specific endorsement or guarantee of any company's product or services.