"In the United States alone, an estimated 4.5 million children ages 5 to 17 have been diagnosed with attention deficit hyperactivity disorder, according to the Centers for Disease Control and Prevention, and rates of diagnosis have risen 3 percent a year between 1997 and 2006. Yet it is unclear what is causing this increase. New research is investigating many avenues. One of them is environmental factors such as pesticides and allergens." This according to a recent article: Do Pesticides and Allergens Cause ADHD, by Mary Beth Sammons on AOL Health.