Impact of Short and Mistimed Sleep on Adolescents With ADHD: The Adolescent Attention and Circadian Timing Study

Inclusion Criteria: * Ages 13-17 years at time of informed consent/assent * Based on semi-structured clinical interview, participants must meet full DSM-5 criteria for ADHD inattentive or ADHD combined presentation. Exclusion Criteria: * Non-traditional school setting (morning-afternoon Monday-Friday). * Exclusionary diagnoses. We will exclude adolescents with known intellectual disability, autism spectrum disorder, psychosis, bipolar disorder, or neurologic conditions (e.g., epilepsy), per caregiver-report. * Exclusionary sleep disorders. We will exclude adolescents with symptoms of obstructive sleep apnea or periodic limb movement disorder based on published cutoffs on a validated questionnaire. * High caffeine intake. To promote adherence to directives not to consume caffeine the day of office visits without withdrawal effects, adolescents with daily intake of \>1 coffee or "energy drink" or \>2 caffeinated sodas per day based on caregiver- and adolescent-report will be excluded. * Unwillingness or inability to take part in study procedures (e.g., visits, prescribed sleep conditions). * Medication use or unwillingness to discontinue melatonin and/or stimulant medications during the 3-week study protocol. * Refusal to refrain from automobile driving during the sleep restriction condition. * "Intermediate" Chronotypes (neither morning larks nor night owls) based on habitual sleep timing on nights when adolescent has no morning obligations such as school or work.