Trajectories of Response to Treatments in Children with ADHD and Word Reading Difficulties

This study investigated patterns of response to intervention in children with co-occurring attention-deficit/hyperactivity disorder (ADHD) and reading difficulties (RD), who participated in a randomized clinical trial examining the efficacy of reading intervention, ADHD treatment, or combined treatments. Growth Mixture Modeling (GMM) was used to investigate trajectories of parent and teacher academic impairment ratings and child oral reading fluency, and whether trajectories were predicted by pre-treatment covariates (ADHD severity, reading achievement, phonemic awareness, rapid letter naming, anxiety, oppositional defiant disorder), for 216 children with ADHD/RD in 2^nd-5^th grade (61.1% male; 72.2% African American; 8.8 ± 1.3 years of age). GMM revealed three trajectories for academic impairment (6.9–24.2% stable, 23.7–78.7% moderately improving, and 14.1–52.1% steeply improving) and oral reading fluency (20.8% low improving, 42.1% moderate improving, and 37.1% high improving). Children in the reading intervention were more likely to be in the stable or moderately improving trajectory than those in the ADHD and combined treatments, who were more likely to be in the steeply improving trajectory for academic impairment. Relative to the ADHD intervention, children in the reading intervention were more likely to be in the high improving trajectory than the moderate or low improving trajectory for oral reading fluency. Children without comorbid anxiety and with better reading skills showed a more positive treatment response for teacher-rated academic progress and oral reading fluency. Results highlight the importance of examining individual differences in response to reading and ADHD interventions. Intervention modality predicted differences in parent/teacher ratings of academic progress as well as reading fluency.