The study was conducted by a team of researchers at the University of Cincinnati and published in Archives of Pediatrics. The researchers examined the results of the “ADHD Collaborative” — a initiative in the greater Cincinnati region aimed to improve the adherence of ADHD treatment guidelines by local community pediatricians. The study included 785 children between 7-11 years of age treated by 158 community physicians from 47 separate practices in greater Cincinnati. The children were evaluated when they first started treatment and 3, 6, 9, and 12 months later. The researchers were interested in examining the effectiveness of the treatment in reducing ADHD symptoms and reducing functional impairment (i.e., how the children did at school, home, and with their peers).

The initial results were very promising.

As you can see above, the treatment resulted in a rapid and dramatic decrease in ADHD symptoms as reported by both parents and teacher. This is consistent with most research on the effectiveness of ADHD medications: they are very effective in reducing ADHD symptoms.

On first impression, the picture became less rosy, or better said, outright gloomy, when the authors examined the effects of the treatment on functional impairment. See for example the effect of the treatment on academic difficulties in reading, math, writing, and overall school performance:

The number of children experiencing impairment in reading, math, writing, and overall in school remained virtually identical during the entire year of the study. This suggests that the intervention did not have much of an impact on the kids’ school functioning. The same pattern of results was observed for the kids’ peer, sibling, and family relations.

Does this mean that medication for ADHD is simply ineffective? Not really. What it means is that medication alone may not have a significant impact on the child’s functional domains.  It is possible that medication provides the foundation for additional interventions to work. However, there is a more relevant limitation of this study. If you compare the two graphs above, you will see that the Y axis of the first graph refers to symptoms of ADHD. In contrast, the Y axis of the second graph refers to the % of children showing impairment in those categories. Why is this significant? Because the first graph allows us to observe changes in a continuous scale of symptoms (we would see even a small change in symptoms). However, the graph below does not allow us to see the effect of the medication on the LEVEL of impairment of the children. That is, we only see that the percentage of children who show impairment did not change, but it is still possible that these children improved significantly!- albeit still performing in the impaired range. So although it is disappointing that the treatment alone did not result in a reduction of the percentage of children who had functional impairment, the picture may not be a gloomy as we think.

The reference:
Epstein, J., Langberg, J., Lichtenstein, P., Altaye, M., Brinkman, W., House, K., & Stark, L. (2010). Attention-Deficit/Hyperactivity Disorder Outcomes for Children Treated in Community-Based Pediatric Settings Archives of Pediatrics and Adolescent Medicine, 164 (2), 160-165 DOI: 10.1001/archpediatrics.2009.263

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The authors of the Journal of Child Psychology and Psychiatry study examined participants from two independent longitudinal studies of ADHD. The first study started in the 1980s and included 140 6-to-17 year-old boys with ADHD, 206 siblings, 280 parents, and 120 non-ADHD peers. These kids were assessed for up to 10 years after the initiation of the study. The second study started in 1993 and included 140 6-to-17 year-old girls, 183 siblings, 274 parents, and 122 non-ADHD peers. These girls were followed for up to 5 years. The final sample for the study included 143 ADHD girls and 147 ADHD boys. Both groups were on average approximately 11 years old at the time of the first assessment. However boys were significantly older (mean age 19) at the time of the last followup compared to the girls (mean age 16).

The ADHD diagnoses were obtained via a 3-step procedure that included a comprehensive psychiatric interview. This greatly limits the possibility that some of the ADHD cases included in the study were misdiagnoses. An similar assessment of ADHD symptoms and co-morbid conditions were conducted during the follow up period.

The Results:

1. As you can see from the graphic below, the authors found that ADHD symptoms decline with age in a non-linear fashion. Specifically, the decline in symptoms accelerates with age.

2. As also noted in the graphic below, girls had significantly more ADHD symptoms than boys across all developmental periods. While in the graphic it looks like this difference was more pronounced during early childhood, the statistical analysis conducted indicated that the sex difference in ADHD symptoms was consistent (the same) at all ages.

Developmental course of ADHD

3. The authors also found a sex difference in the developmental progression of co-morbid conditions. Specifically, while in childhood ADHD in boys and girls were associated with the same co-morbid conditions (Mood Disorders, Disruptive Behavior Disorders, and Anxiety), during adolescence ADHD was no longer associated with anxiety for boys. In contrast, girls continued to show high co-morbidity between ADHD and anxiety in adolescence.

Psychiatric Co-morbidity of ADHD

The good news is that ADHD symptoms appear to decrease with age, and that this decline accelerates as children get older. However, the news are not as good for girls. The study shows that symptoms in girls appear to be more severe than in boys, and that for girls there are more co-morbid conditions during adolescence than for boys. While this may suggest that ADHD is more severe in girls than in boys, we should keep in mind that the results of any study is highly dependent on the sample used, and more importantly the way participants were recruited. For example, boys and girls in this study came from two independent samples, and unknown methodological differences between these samples could be driving some of the results. In addition all of the participants with ADHD were initially included after getting a clinical diagnosis for ADHD by a referral source, which was later confirmed by the study’s own clinician (details on how the recruitment took place were not provided). Therefore, it is possible that these findings reflect sex differences in the initial clinical identification of ADHD by the kid’s clinicians. Specifically, it is possible that girls who were diagnosed and subsequently entered the study simply did so because of experiencing more severe symptoms. While indeed there are some methodological limitations, this is one of the only studies who have provided comprehensive empirical data that help us understand the differences between boys and girls in the progression of ADHD symptoms and co-morbid conditions during childhood and adolescence.

The reference: Monuteaux, M., Mick, E., Faraone, S., & Biederman, J. (2009). The influence of sex on the course and psychiatric correlates of ADHD from childhood to adolescence: A longitudinal study Journal of Child Psychology and Psychiatry DOI: 10.1111/j.1469-7610.2009.02152.x

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