Electrophysiological Effects of Guanfacine Extended Release in Attention Deficit Hyperactivity Disorder (ADHD)

All subjects with the study will be children (age 6-12) with Attention Deficit Hyperactivity Disorder (ADHD). After baseline assessment confirms the presence of ADHD, children will have an Event related potential (ERP) (a type of electroencephalogram \[EEG\]) study. After the baseline EEG, children will be randomized to either placebo or GXR for a 4-week, parallel groups trial. During this trial, dosing will be flexibly adjusted according to patient response or presence of side effects. The dosage will range from 1-4 mg. At the end of the four week trial, a follow up ERP study will be obtained. Our hypotheses are: A) GXR will be superior to placebo at reducing symptoms of ADHD as measured by standardized clinical diagnostic tools by week 3 of treatment. B) Compared to placebo and pretreatment measures, GXR at week 4 of treatment will increase the amplitude of the right frontal N200 and frontal-central P300, and such changes will correlate with clinical response.