Abnormal iron levels in the brain may be a biomarker for ADHD
A recent study found that patients with ADHD who have NOT had psychostimulant medication (like Ritalin) have much lower iron levels than those with ADHD who HAD used the meds and healthy children and adolescents, indicating that psychostimulant meds may normalize brain iron levels.
http://www.medicalnewstoday.com/articles/278362.php