Saved by the bell: A neurobiological investigation of the protective effects of delayed high school start times in youth with and without ADHD - PROJECT SUMMARY/ABSTRACT Youth in high school typically do not get enough sleep, and this lack of sleep can exacerbate the academic challenges of starting high school, as well as the risk for poor mental health, which is already elevated in this period. Youth with attention-deficit/hyperactivity disorder (ADHD), who make up ~9% of high school students, are more likely to struggle academically, develop comorbid mental health problems, and experience poor sleep compared to their peers. This combined risk makes the transition to high school an especially vulnerable period for youth with ADHD. Delaying high school start times is one approach to alleviate sleep-related challenges that youth face when starting high school, and there is mounting evidence suggesting that delayed start times improve academic and health outcomes. Critically, the neurobiological and behavioral mechanisms conveying the benefits of delayed school start times are still unclear. Further, it is unknown if youth with ADHD will see enhanced benefits from delayed school start times. This proposal will address these gaps by capitalizing upon a Florida state law mandating a delay in high school start times to no earlier than 8:30am in the 2026-2027 school year. To leverage this upcoming change, we propose a two-cohort quasi-experimental design with an ‘early-start’ (7:30am) cohort of 9th grade students to be collected in the 2025-2026 school year and a ‘delayed-start’ (8:30am) cohort to be collected in the 2027-2028 school year. Each cohort will include 50% youth with ADHD, and we will conduct a follow-up assessment of 80% of each cohort in 10th grade. Using rich behavioral data and sophisticated modeling of functional MRI (fMRI) data, we will test the following hypotheses: First, the delayed-start cohort will have better subjective and objective sleep, more structured morning routines, fewer mental health problems, including ADHD symptoms, and better academic achievement (Aim 1). Second, during resting state and reading fMRI tasks the delayed-start cohort will have more segregation between opposing brain networks that facilitate externally- and internally-focused attention (dorsal attention and default mode, respectively), as well as more integration of these two networks with a third network (fronto-parietal) that flexibly orchestrates the balance between the two attention-related networks (Aim 2). Third, youth in the delayed-start cohort will see more developmentally-appropriate changes in brain networks, increased grades, and decreased mental health problems in the transition from 9th to 10th grade (Aim 3). Throughout our aims, we hypothesize to see greater benefits of delaying school start times in youth with ADHD. Together, the findings from the proposed project will clarify how delaying school start times protects youth with and without ADHD during a pivotal transition period and, critically, will provide evidence for how delayed start times confer benefits to short- and long-term outcomes via modulation of sleep quality, morning routines, and functional brain networks supporting attention. This proposal stands to provide a comprehensive characterization of large-scale policy changes impacting youth during a vulnerable period.
