Sensitivity of the NIH Toolbox to Stimulant Treatment in Intellectual Disabilities

The XRMPH or matching placebo will be started at a dose of 0.3 mg/kg/day and individually titrated over two weeks. Phone calls at the end of weeks 1, 2, and 3 will be used to collect adverse event and response data. If there is no evidence of side effects and ongoing symptoms of ADHD, the dose will be increased to 0.5 mg/kg/day at one week and 0.7 mg/kg/day at 2 weeks (maximum dose of 60 mg per day consistent with FDA labeled use in youth).