1 - (SYM 80) Examining the Effects of Treatment Engagement for a High-school-based Training Intervention for Adolescents with ADHD

The Challenging Horizons Program (CHP) is a multi-component school-based training intervention for secondary students with ADHD delivered in twice weekly sessions across an academic year. Intent-to-treat (ITT) analyses revealed positive effects of the CHP overall. However, wide variability in treatment attendance indicates that inclusion of individuals with low doses of treatment may obfuscate conclusions about treatment effectiveness from ITT analyses. We used propensity-score methods to examine the complier average causal effect (CACE), or the effect among those who engaged with treatment relative to similarly-weighted control participants, accounting for variables possibly associated with treatment engagement (e.g., socioeconomic status, race, ethnicity, symptom severity). Participants were 186 high school aged adolescents (65% non-Hispanic White; 79% male) with a diagnosis of ADHD who were randomly assigned to the CHP or community control. Outcomes included parent-rated academic functioning, parent- and self-rated social-emotional functioning, and GPA. The CACE was estimated using propensity-weighted models for youth engaging in ≥30 CHP individual sessions (15-20 min) across the academic year. Most (78%) CHP participants engaged in ≥30 sessions. CACE analyses using latent growth curve models revealed significant effects among treatment engagers across ratings of academic and social outcomes relative to similar control participants. For most outcomes, CACE estimates were larger than those found in ITT analyses, especially at 6-mo follow-up. Engaging in 30 or more individual CHP sessions appeared to be an attainable threshold associated with incremental gains across several academic and social outcomes. Effects of CHP engagement were amplified at 6-mo follow-up, reflecting the enduring benefits of training interventions. Treatment engagement was not associated with variables such as socioeconomic status, race, ethnicity, sex, or baseline severity, highlighting advantages of school-based services for treatment access and engagement. Future work should focus on facilitators of treatment engagement and feasibility of the CHP as delivered by school personnel.