Dose-Optimization Study Evaluating the Efficacy, Safety and Tolerability of Vyvanse (Lisdexamfetamine Dimesylate) in Children Aged 6-12 Diagnosed With ADHD

Inclusion Criteria 1. Subject is a male or female aged 6-12 years inclusive at the time of consent. 2. Females of Child-bearing Potential (FOCP) must have a negative serum beta Human Chorionic Gonadotropin (HCG) pregnancy test at Screening and a negative urine pregnancy test at Baseline and agree to comply with any applicable contraceptive requirements of the protocol. 3. primary diagnosis of ADHD based on a detailed psychiatric evaluation. 4. Subjects must have a baseline ADHD-RS-IV total score ≥28. 5. Subject is functioning at an age-appropriate level intellectually. 6. comply with all the testing and requirements. 7. Subject is able to swallow a capsule. 8. Subject has blood pressure measurements within the 95th percentile for age, gender, and height. Exclusion Criteria 1. Subject has a current, controlled (requiring a restricted medication) or uncontrolled, comorbid psychiatric diagnosis with significant symptoms such as Post Traumatic Stress Disorder, psychosis, bipolar illness, pervasive developmental disorder, severe obsessive compulsive disorder, severe depressive or severe anxiety disorder or other symptomatic manifestations. 2. Subject has Conduct Disorder. 3. Subject has a documented allergy, hypersensitivity, or intolerance to amphetamines. 4. Subject has failed to respond to one or more adequate courses (dose and duration) of amphetamine therapy. 5. The subject has a recent history (within the past 6 months) of suspected substance abuse or dependence. 6. Subject has a positive urine drug result. 7. Subject weighs less than 50 pounds (22.7kg). 8. Subject is significantly overweight. 9. Subject has a history of seizures (exclusive of febrile seizures), a tic disorder, a current diagnosis and/or family history of Tourette's Disorder. 10. Subject has any reported history of abnormal thyroid function. 11. Subject has taken another investigational product or taken part in a clinical trial within 30 days prior to Screening. 12. Subject has a concurrent chronic or acute illness (such as severe allergic rhinitis or an infectious process requiring antibiotics), disability, or other condition that might confound the results of safety assessments. 13. The female subject is pregnant or lactating. 14. Subject is well-controlled on their current ADHD medication with acceptable tolerability.