Dr. Mark Stein has been an active clinical researcher specializing in ADHD for over 25 years. He started the Hyperactivity, Attention, and Learning Problems (HALP) Clinic at the Institute for Juvenile Research, University of Illinois at Chicago, where he is a professor in the departments of psychiatry and pediatrics. Between 1977 and 2002, Dr. Stein was a professor of psychiatry at the University of Chicago, chair of psychology at Children's National Medical Center, and professor of psychiatry and pediatrics at George Washington University Medical School in Washington, DC.

Dr. Stein has written over 70 articles on ADHD and co-edited the textbook Attention Deficits and Hyperactivity in Children and Adults (Marcel Dekker, 2000). His work has been featured in various media outlets. He has conducted numerous studies of ADHD medications, and their effects and side effects. Current research is on pharmacogenomics, measuring and predicting response to ADHD medications, managing ADHD in primary care settings, and sleep problems.