We are conducting a study on Attention-Deficit Hyperactivity Disorder (ADHD) using (6-16 years) identical twins.

We are looking for very rare pairs of identical twins where only one twin has ADHD and the other does not (discordant pairs). We are also looking for more common pairs of identical twins where both twins have the diagnosis of ADHD (concordant pairs). The study involves a visit to the NIH in Bethesda, Maryland, and includes questionnaires, computerized tests, paper and pencil tests, a blood test, and Magnetic Resonance Imaging (MRI) scans of the brain. Travel and accommodation expenses are available.