Although stimulant medication treatment has been shown in hundreds of studies to produce significant reductions in ADHD symptoms, it's impact on children's academic outcomes remains unclear.  Certainly, research has shown that medication treatment frequently yields short-term improvements in the accuracy and amount of academic work that children complete. However, documenting that this translates into long-term gains in academic achievement has remained elusive.  This is an important gap in the literature because problems with academic achievement are a frequently occurring difficulty in children with ADHD.

A study published in a recent issue of the Journal of Attention Disorders [Barnard, L., et. al., (2010). The importance of ADHD subtype classification for educational applications of DSM-IV. Journal of Attention Disorders, 13, 573-583] offers perhaps the most careful examination to date of how stimulant medication treatment impacts academic achievement over time.  As such, this is an important study to be aware of.

Participants were drawn from a nationally representative study commissioned by the US Office of Special Education Programs to examine academic outcomes in students eligible for special education services.  From the nearly 10,000 6-12 year old youth in this sample, 2844 carried a diagnosis of ADHD.  All participants were administered a standardized test of academic achievement - the Woodcock Johnson III - that evaluated their achievement in reading and math in relation to age-match national norms.  The WJ-III was administered 3 times over a 4-year period.  This enabled the researchers to examine how children's level of academic achievement changed over time.


- Diagnosis of ADHD -

It is important to understand how children were identified with ADHD in this study.  Parents were simply asked whether their child had been diagnosed with "...attention deficit disorder or attention deficit hyperactivity disorder?  These are sometimes called ADD or ADHD."  If parents responded affirmatively, this diagnosis was confirmed with the child's school, as it would be part of the educational record for children receiving special educational services.

The important point here is that there was no independent verification that the diagnosis given to the child was correct, and it is likely that many children may have been misdiagnosed.  The implications of this point will be evident below.


- Medication treatment status -

To measure stimulant treatment status, parents were asked at 3 time points whether their child was receiving medication treatment for ADHD.  Children taking medication at all 3 time points were considered the 'treated' group and those never receiving medication were considered the 'untreated' group.  Children receiving treatment at 1 or 2 of the time points were not included so that a 'pure' group of treated and untreated children could be compared. 

Children in both treated and untreated groups received whatever educational supports would have been provided in their schools to students with ADHD and are assumed to have been equivalent across groups.   Thus, comparisons of their academic achivement indicate benefits that may have been associated with medication treatment above and beyond whatever other services they were receiving.


- ADHD subtype -

The researchers were interested in how medication treatment might impact academic achievement in children with the 3 different subtypes of ADHD - the inattentive type (children with significant attention difficulties but fewer problems with hyperactive and impulsive behavior), the hyperactive-impulsive type (children with significant hyperactive and impulsive behavior but fewer attention difficulties) and the combined type (children with both attention problems and hyperactive-impulsive behavior).

To identify subtypes, the researchers examined teacher ratings on items that asked about the different types of ADHD symptoms.  These ratings were used to group children into each of the 3 subtypes, depending on which types of symptoms were most prominent.  Of course, this is not an ideal method for accurate subtyping, but was the best the researchers could do given the data that was available to them.

Interestingly, 17% of the children did not show prominent elevations of either inattentive or hyperactive-impulsive symptoms, even though they were reported to have an ADHD diagnosis.  Thus, they did not fit into any of the 3 subtypes, and were instead classified as having ADHD, NOS (not otherwise specified). 

Because these children did not show the kind of significant problems with inattention or hyperactive-impulsive behavior that is generally seen at school in children with ADHD, it must also be considered that they had been incorrectly diagnosed in the first place.  Or, they may have simply had a milder form of the disorder.


- Results - 

Compared to untreated children, those receiving medication treatment generally showed significantly greater gains in academic achievement over time.  However, this was only true for children in the 3 well-defined subtypes of ADHD, i.e., inattentive, hyperactive-impulsive, and combined, and not for those in the NOS group.

Medication treatment appeared to be associated with greater achievement gains for children with high levels of attention problems - those with the inattentive or combined subtypes - compared to the gains made by those with the hyperactive-impulsive subtype.  Thus the gains associated with medication treatment were twice as large for inattentive children than hyperactive-impulsive children, and nearly three times as large for children with the combined subtype compared to the hyperactive-impulsive subtype.  In all cases, however, the gains were small to moderate in magnitude.

Interestingly, not only did children in the ADHD, NOS group fail to show significant benefits from medication treatment, but treatment for this group was actually associated with reduced academic achievement over time.  And, the magnitude of the negative effect was as large as any of the positive effects found for medication treatment in the other 3 subtypes.


- Summary and Implications -

This is an important study for several reasons.  First, it is one of the few studies to show that ADHD medication treatment provided over an extended period is associated with significant gains in children's academic achievement. The fact that this was found in a large and nationally representative sample of children treated in the community, and not as part of a carefully conducted research study, is also noteworthy.  This implies that sustained medication treatment as provided in community settings can have positive effects on children's academic performance.  Thus, the authors suggest that the "...overall implication for parents and practitioners is ... that stimulants are not just for the management of behavior but can be associated with positive academic outcomes also."

Of course, it should be emphasized that these positive findings in no way suggest that consistently administered medication treatment is all that children need to promote their academic success. As noted above, the magnitude of the gains associated with medication treatment were modest at best, and specific academic supports will be required by many children with ADHD in order to achieve at a level consistent with their potential.

The negative association between medication treatment and children in the ADHD, NOS group is also important and a reason for concern. Recall that children in this group failed to show extreme teacher ratings for either attention problems or hyperactive-impulsive behavior, suggesting that they either had a milder form of ADHD or that they had been incorrectly diagnosed. 

Two possibilities are suggested.  First, stimulant medication treatment in children with milder variants of ADHD may not be advisable as it could be associated with reduced academic achievement over time.  Why this might be the case, however, is unclear. 

A second possibility, and my own view is that this is more likely, is that when children are incorrectly diagnosed with ADHD, medication treatment may hurt their performance over time because whatever actual difficulties they have are not being addressed.  For example, if a child with a learning disability is misdiagnosed with ADHD and treated with medication, he/she would not receive the specialized academic supports/instruction required to help them make good academic progress.

Despite the interesting nature of these findings, there are important limitations to this study that should be recognized.  Most noteworthy is that standardized diagnostic evaluations were not conducted on many of the children, which is likely to introduce error into the findings.  Related to this is that the researchers had to rely on teachers' ratings of a small number of behaviors to assign children to the different ADHD subtypes, which is far from ideal and would also introduce error. This was a limitation of the data set was available for the authors to work with, and was not something they could overcome.

These shortcomings notwithstanding, results from this study highlight the need for careful diagnosis as well as the need to carefully monitor how medication treatment may affect children's academic achievement over time.  Although encouraging evidence was provided that such treatment can help enhance some children's long-term academic achievement, not all children diagnosed with ADHD will show such benefits and some are actually likely to be harmed.