Approximately 4 percent of adults in the United States have attention deficit hyperactivity disorder (ADHD), yet less than 20 percent of those have been diagnosed or treated. What does this mean for employers and HR professionals? Belynda L. Gauthier is a longtime HR professional and board president of CHADD (Children and Adults with Attention-Deficit/Hyperactivity Disorder), the national nonprofit organization for children and adults with ADHD.