ADHD is a disorder that affects attention, hyperactivity, and impulsivity. It is most commonly diagnosed in children aged 4-16. Recent research has found that ADHD is linked to differences in brain structure and function compared to those without the disorder. Studies have shown that children with ADHD have less surface volume in areas of the thalamus involved in regulating reactions, as well as differences in the pulvinar nucleus which is involved in attention. Medication has been found to increase surface volume in these areas, suggesting ADHD has a neurological basis.